US1766936A - Telephone system - Google Patents

Description

June 24, 1930. o. A. PEARCE TELEPHONE SYSTEM Filed Sept. 27

, 1928 10 Sheets-Sheet 1 noa o A. o o

o o o o uuoo Iml'n'fi Ehuan Huts Pearce O. A. PEARCE TELEPHONE SYSTEM June 24, 19530.

Filed Sept. 27, 1928 10 Sheets-Sheet 2 [nu ET or" I Umen Huis Pearce p June 24, 1930. o. A. PEARCE 1,766,936

TELEPHONE SYSTEM Filed Sept. 27, 1928 Sheets-Sheet 3 5 IZI ITTTITLITJ? Um'en Fiuzs Pearce June 24, 1936. PEARCE 1,766,936

TELEPHONE SYSTEM Filed Sept. 27, 1928 1o Sheets-Sheet 4 In'uen'hr' Umeu Huis Pear-ca June 24, 1930- PEARCE 1,766,936

TELEPHONE SYSTEM- Filed Sept... 27, 1928 10 Sheets-sheaf 5 lnvenlur' Umen FI ris Pearce June. 24, 1930.

10' Sheets-'-She et 6 ITTEW Umen Huis 'PEETCE TELEPHONE SYSTEM Filed Sept. 27, 1928 10 Sheets-Sheet 7 Inuuninr Uznen Huis FE arcs June 24, 1930' Q PEARCE 1,766,936

TELEPHONE SYSTEM Filed Sept. 27, 1928 10 Sheets-Sheet a Ifiuentuv" Umen Huts Pearce June 24, 1930. O. A. PEARCE 1,766,936

TELEPHORE SYSTEM Filed Sept. 27, 1928 10 Sheets-Sheet 9 Inusniur Umen Fhris Pearce June 24, 1930. o. A. PEARCE 1,765,936

TELEPHONE SYSTEM Filed Sept. 27, 1928 10 Sheets-Sheet l0 Umen Flu-is Pearce Patented June 24, 1930 hairs PAT.

OVEN AVIS PEARCE'OF LlYVERPOOL, ENGLAND, ASSIGNOR TO ASSOCIATED TELEPHONE AND TELEGRAPH COMPANY, OF KANSAS CITY, MISSOURI, A CORPORATION OF DELAWARE Application filed September 27, 1928,. Serial No.

The present invention relates to tele phone systems and is more particularly concerned W'th so-called routining apparatus, that is to say, apparatus designed to simulate for test purposes the conditions which will be encountered by certain apparatus under normal conditions of working and to give an indication of any irregularity which may occur due to faulty operation of the apparatus. The arrangement according to the present invention is particularly applicable to the testing of apparatus used in the setting up of calls from automatic to man ual exchanges with call indicators at the manual operators positions.

It has been found desirable in some cases to transmit the wanted number over the trunk line to the manual exchange in code in order to save time, and in this case it is necessary to have a register switch at the automatic exchange to receive the impulses from the calling party and to convert them into tl e appropriate code pulses. Conveniently, this is done as in the arrangement shown in British Patent No. 229,371 by employing a repeater at the outgoing end of the trunk line, the repeater being provided with arrangements for associating with itself a suitable register sender conveniently termed a coder.

The present invention will be described in connection with the testing of such a repeater and it will be appreciated that the test must include the transmission to the coder of a suitable test number and the checking of the code impulses sent out therefrom in response to the re istration of this number. V

In a telephone system in'which calls from an automatic subscriber are routed to a manand described in British Patent No. 268,058

with the exception of the addition of a further switching relay for routining facilities,

TELEPHONE SYSTEM 308,754, and inGreat Britain October 10, 1927.

the full purpose of which will be apparent from the detailed description which follows later.

The routiner is arranged to simulate the working conditions normally imposed on these repeaters and to check the correct functioning of the repeater at each stage of the call, together with such features of the reg ister sender as are necessary to completely follow working conditions. Further, the tests imposed include arrangements to check the condition of the outgoing junction with which the repeater is associated to provide a transmission 'test through the repeater transmission bridge, to test for the correct metering condition, to check the operation of the repeater on receipt of a-busy signal, and to test for the guarded condition during release of the circuit. In addition, marginal limit tests are applied to certain of the repeater relays, for example, the impulses accepting relay so that the correct adjustment of such important relays may be verified, in addition to the test under average working conditions. i p

The routining equipment is arranged to deal successively with a large number of repeaters,in the case of the drawings attached hereto as many as 960. Access to the repeaters is obtained essentially by means of primary and secondary distributors of which there are shown in the drawings two primary distributors having access to 48 secondary distributors each of which is arranged to deal with20 repeaters. The arrangement of this distributing apparatus is substantially identical to that describedin British Patent -No. 292,691 and it will be readily obvious to those versed in the art that this arrangement may be extended if desired so that access may be obtained to whatever number of repeaters may be equipped at any particular exchange.

The general scheme of operation is, briefly, that once the routiner is started, each repeater in turn is subjected to a series of tests and the operation continues automatically until all have been dealt with unless a fault is found. In this case the routining operation is stopped and suitable lamps indicate the particular repeater on which the fault has been found and also the nature of the fault.

In order that the invention may be more fully understood a detailed description will now be given, reference being had to the accompanying drawings comprisingFigs. 1 to 10, inclusive, which show by means of the usual circuit diagrams sufficient ofthe aprparatusemployed to enable the invention to be understood. it will be understood, however, that this is given by way of example only, and that various modifications may=be made in the circuit details by those skilled in the art without departing from the spiritor exceeding the scope of the invention. These drawings shouldbe arranged with Fig.2 to the right of Fig. 1, Figs. 3, 5, 7 and 9 below Fig. 1, and each other in order, andFigs. 4, 6, 8 and below Fig. 2, and each other in order with the interconnecting lines in alignment. Figs. 1 and 2 show two primary distributors PD and PD and a secondary distributor SD, while it willbe understood that other secondary distributorsnot shown are connected to the banks of the primary distributors PD and PD Fig. 3 shows the control switch G8 which controls the connection of each testing condition, while the remaining figures show various relays associated with the invention together with sundry keys included for purposes which will be followed from the detailed description hereafter.

A description will first be given of the operation of the distributor equipment. lVhen it is desired to start the routining tests the start key .10 (Fig. 10) is operated, thereby causing'the operation of relays S and SS over the -ircuits: earth, key 10 in operated position, conductor 11 to the winding of relay S (Fig. 6) to battery; and earth, key 10, conductor 12 to relay SS (Fig. 4) to battery. When relay S operates, earth pulses for instance at the rate of 10 per second are connected from conduct-or 19 (Fig. 4) resting springs of step-0n key 13, armature 14 and back contact, conductor 15, armature 16 and front contact 6) armature 17 and back contact, armature 18 and back contact, winding of relay P -to battery. Relay P now operates in synchronism with the earth pulses. Furthermore, earth pulses at conveniently the rate of .40 per minute are connected from conductor 20 (Fig. 6) armature 21 and front contact, armature 22 and back-contact, winding of relay DR (Fig. 6) to battery. Relay DR pulses over the circuit described, throughout the remainder of the test, or until the alarm relay AM is operated.-

Returning now to relay P which it will be remembered is pulsing, on its first energization earth is extended from armature 23, conductor 24, armature 25 and back contact, conductor 26, armature 27 and back contact, conductor 28, upper winding of relay DA (Fig. 4) to battery. Relay DA closes its light armature 29, and the lower winding is held short-circuited until relay P restore Earth is connected to the right hand terminal of the lower winding of relay DA. over back contact and armature 25, conductor 24, armature and front contact '23 and earth is connected to the left-hand terminal of the lower winding of relay DA over armature 29 and front contact, conductor 30, front contact and armature 31. On the restoration of relay P, relay DA operates all its armatures both its windings being energized in series over the following circuit: earth, armature 31 and front con tact (Fig. 6), conductor 30, front contact and armature 29 (Fig. 4), lower winding of relayDA, conductor 26, armature 27 and back contact (Fig. 6) conductor 28, upper winding of relay DA to battery.

On the next energization of relay P two circuits are completed, the first as follows: earth, armature 23, conductor 24, armature 25 and front contact, (Fig. 4), armature 32 and back contact, conductor 33, winding of relay TC (Fig. 6) to battery, and parallel thereto, from conductor 33, over armature 34, upper winding of two-step relay DB to battery. Relay TC operates fully, and relay DB closes its light armature 38, its lower winding being then short-circuited until relay P restores, since earth is connected to its left-hand terminal as follows: earth, armature 31 and front contact, armature 39 and back contact, armature 38 and front contact, and to the right-hand terminal-as follows: earth, armature 23, conductor 24, armature 25 and front contact, armature 32 and'back contact, conductor 33, armature 34 and front contact, conductor 35, armature 36 and back contact, conductor 37, to right-hand terminal. The second circuit is from earth, armature 40 (Fig.6) conductor 41, armatures 42, 43, 44 and 45 (Fig. 4), conductor 46 (Fig. 3), wiper 47 of primary distributor PD (Fig. 1) bank contact 1, conductor 48, winding of driving magnet DM of secondary distributor SD to battery. The magnet energizes and remains energized until relay P releases, at the end of the pulse, whereupon it moves the wipers of the secondary distributor forward one step so that they are now in contact with the repeater circuit in readiness for the commencement of the test. The release of relay P also removes the short circuit from the lower winding of relay DB, and relay DB operates all its armatures since both its windings are now energized in series over the following circuit: earth, armature 31 of relay S, armatures 39 and 38, lower winding of relay DB, conductor 37, armature 36, conductor 35, upper winding of relay DB to battery. The operation of relay DB gizing circuit at armature s4 and prepares various other circuits for the commencement of the routine test. It will be seen that relays P and DA cannot re-operate to step the secondary distributor until relay DB is released, and relay DB is now controlled by relays TO and EA.

The operation of start relays S and SS when the start key was thrown effects a number of circuit changes which will be described later.

Itwill be sufficient here to point out that the homing circuits of the Various distributor switches are opened at armatures L9, 50, 51, 52, 53, 54: and 55 of relay SS and that earth is connected over armature 54: and front contact, armature 156, conductor 57 wiper 58 of primary distributor PD and its first bank contact to the first group indicating lamp 59 to battery, to show the group in which the repeater under test is located. Moreover, earth is extended from wiper 60 of the secondary distributor SD to the first individual indicating lamp 61, so that the lighting of these two lamps will always show exactly which repeater is under test.

. The leads to the individual indicating lamps it will be understood. are multiplied in the corresponding banks. of all secondary dise tributors.

The routiningoperation will now co1nmence and will proceed in a manner tobe described shortly, and when it is completed the wipers of the control switch CS (Fig.

. 3) will be on contact 23, and relay TO will operate from earth, springs controlled by armature 62 of relay KA (Fig. 8) conductor 7 63, armature 6e and front contact,'conductor 65, resting springs ofreset key 66, conductor 67 (Fig. 10, 8,7, 5 and 3), wiper 68 of. control switch CS resting on bank contact .23, conductor 69 (Figs. 3, 5 and 6) winding of relay TO to battery. The operation of relay TO opens contacts 39 and thus breaks the circuit of relay DB which releases thereby allowing contacts 17 to close.

The earth impulses from conductor .19

(Fig. 4) are riow extended to relay P as before, and it operates thus energizing the upper winding of the two-step relay DA which operates completely when relay P restores at the end of the pulse. The further operation of relay P, DA, DB and TC and the stepping of the secondary distributor so a circuit as follows: earth,

that the testing conductors are connected to I the next repeater is similar to that described previously.

The full operation of relay DB completes springs controlled by armature 62 of relay KA, (Fig.

8), conductor; armature 64 and front nects earth from armature 70, conductor 71,

first bank contact and wiper 72 of control switch CS (Fig. interrupter springs .73, winding, of driving magnet DM tov battery, thus causing the control switch to step its wipers to the first position in readiness for the next test cycle.

Relay DB will again remain locked up after the secondary. distributor is stepped till the control switch again reaches contact 23 and relay T0 is re-operated.

It will be seen that owing to the advance of the secondary distributor, the second individual indicating lamp will :glow whilst the group lamp is not altered. The test new proceeds on this repeater and when it is completed the secondary distributor will take another step in a similar manner. When all the twenty repeaters connected to the banks of the first secondary distributor have been thus dealt with, a circuit is completed for relay TO to operate as before, and in this case the operation ofTO in addition to openin the circuit to relay DB, closes the circuit of relayTS (Fig. l) in parallel with circuit: earth,armature 31- (Fig. 6) conductor 30, armature 79 and front contact, armature 78 and back contact, winding of relay TS to battery.

Theoperation of relay TO, opened the circuit of relay DB at armature 39, allowing relay DB" to release and on the commencement of the next pulse from'relay P, a circuit is completed from earth, armature l0 and front contact (Fig. 6) conductor 41, armature 4-2 and front contact, armature a3 and front contact, back contact and armature 80, armature 81 and back contact, conductor 82, winding of driving magnet DM of primary distributor PD to. battery, so that the magnet is energized.

magnet DM also releases and advances the first six wipers of the primary distributor DM? to battery. The magnet energizes,

hen relay P releases after the pulse, Y

- reaks its circuit at the interrupter springs 85 and releases, thus moving the second six wipers of the primary distributor forward one step. The resultant effect is therefore as ifall twelve wipers of the primary distributor were controlled by one magnet. WVhen relays P, DA and TS are energized a circuit is also completed for the two-step relay DC as follows: earth, armature 23 of ing circuit: earth, armature 87 and front contact, armature 86 and front contact, both windings of relay DC in series to battery. The locking circuit of relay TS is now broken at armature 78 and relay TS releases allowing the next pulse from relay P to be connected to the upper winding of relay DB. Earthis also extended from armature 40 of relay'P, conductor 41, armatures 42, 43, 44 and 45 (Fig. 4), conductor 46, wiper 47 and second bank contact of primary distributor PD to'the magnet of the second secondary distributor (not shown). W'hen relay P releases at the end of the pulse the magnet circuit is broken and the wipers of the secondary distributor are moved into contact with the first repeater in the second group. p

At the same time relay DB operates fully, opening the circuit of relay P at armature 17 and relay DA at armature 27, thus preventing any more stepping pulses and allowing relay DC to release as its circuit is opened by the restoration of relay DA.

It will be appreciated that at this stage the second group lamp is lit, and the first individual indicating lamp is lit, showing that the first repeater of the second group is being dealt with.

The first secondary distributor SD is returned to its home position owing to a circuit completed by relay TS as follows: earth, armature 88, conductor 89, bank contact 20 and wiper 90 of secondary distributor SD, interrupter springs 91, winding of magnet DM to battery. The magnet drives the wipers to the first contact and since this contact is not earthed, further rotation cannot take place. The routining operations on the repeaters accessible over the secondary distributor will now proceed as before, and when all the twenty have been dealt with, the primarv distributor will be advanced a further step, so as to connect up the succeeding secondary distributor. If there are more than 24 secondary distributors as will be assumed in this case,

primary distributor PD 'will come into action. hen the wipers of the primary distributor PD reach the 25th contact, the test leads are extended to the wipers of primary distributor PD and thence to the first secondary distributor of this group. lbloreover, a circuit is completed forrelay DX (Fig. 4) as follows: earth, wiper 92 and 25th bank contact of primary distributor PD conductor 93, armature and front contact 51, winding of relay DX to battery. Relay DX operates and at its armature 81 transfers the stepping circuit to the magnet DM of primary distributor P13 Consequently, when the next pulse for advancing the primary distributor is received PD remains on the 25th contact, and magnet DM advances the wipers of primary distributor PD one step to connect up the 26th secondary distributor i. e. the second one connected to the banks of the second primary distributor.

The subsequent operation of the distributor equipment will be readily understood from the foregoing and when the whole group of repeaters has been dealt with, relay TU (Fig. 6) will operate; this relay being connected to the appropriate contact, for instance, 25, in the bank 94 of the last primary distributor depending upon the number of repeaters to be dealt with. Vfhen the last repeater has been tested, earth is extended from wiper 95 and contact 25 of primary distributor PD conductor 96, armature 53 and front contact, conductor 97, winding of relay TU (Fig. 6 to battery). Relay TU operates and at armature 98 operates alarm relay AM, and at armature 99 lights a lamp'toindicate that the routine test is finished. The operation of alarm relay AM disconnects'the pulsing circuits from relays P and DR at armatures 18 and 22 respectively, and an audible alarm signal is completed via armature 100, this calling the attention of the testing operator, who observing that the routine complete lamp is lit, will restorethe start key 10, thereby allowing the various distributor switches to return to normal. A description will now be given of the actual routining operations performed on each repeater.

It will beremembered that relay DB operates when the secondary distributor steps to connect the testing leads to the first repeater to be dealt with. A circuit is thus completed from earth, springs controlled by armature 62 (Fig. 8), conductor 63, armature 64 and front contact, conductor 65 (Figs. 6, 8, 10 and 9), winding of relay RS to battery. The same earth is also extended via resting contacts of key 66 (Fig. 10), conductor 67, wiper 68 of control switch CS, and is maintained on-this wiper throughout the test cycle in order to provide operatingcircuits for relays associated withthe various testing functions. The operation of relay RS extends earth at its armature 70 over conductor 71, first bank contact and wiper 72 of control switch CS, interrupter springs 73, winding ofDM to battery, thus causing the control switch to step the wipers PHI to the second contacts. lnis earth is also extended from wiper 72 via conductor 101 to the winding of relay TB (Fig. 6) and energized, and relay TC by closing armature 103 extends eartn over conductor 10%, armature 105 and back contact, conductor 106,

upper winding of relay TA (Fig. 7) to bat tery. Relay TA operates over this circuit and opens armature 107, thus removing the earth which is connected to the second contact of the bank swept. over by wiper72 of the control switch CS in the following circuit: second contact, conductor 117, armature 107 and back contact, conductor 67 (Figs. 7, 8 and 10) resting contact of spring 66, conductor (Figs. 10, 8 and 6) front contact and armature 6i, conductor 63, springs controlled by armature 62 to earth. At armature 108 relay TA connects its lower winding over conduct r 109, arinas ture 113 and baclr contact (Fig. conductor 109, wiper 110 of primary distributor PD and its first bank contact, conductor 111, wiper 112 and its first bank contact to the private lead or" repeater selected. If the re peater to which the secondary distributor is connected is busy at this time, relay TA. will remain held up over its lower winding until earth is removed from the release trunk conductor when the repeater reverts to common use. Thereupon relay TA de-energizes and at armature 108 and back contact again applies earth to the release trunk conductor to busy the repeater to its normal means of access. This guarding earth is derived from armature 31 (Fig. 6) ,conductor 11%, back contact and armature 115 (Fig. 7), baclr contact and armature 116, back contact and armature 103, conductor 109 (Figs. 7, 8, 6 and armature 113 and back contact, conductor 409 (Figs. 1, 3 and 1) wiper 110 and its first bank contact, conductor 111, wiper 112 and its first bank contact to the private lead of the repeater. Upon the release of relay TA, earth over conductor 67 is connected via armature. 107 (Fig. 7), conductor 117, contact 2 and wiper 72 of control switch CS, interrupter springs 73, winding of driving magnet PM to bati tery, thus stepping the control switch to the third contact as soon as the repeater is ture 120 of thestart relay S over conductor- 119, and thereforeas the control switch is advanced step-by-step at the satisfactory conclusion of each test, successive indicating lamps are lit, showing at a glance exactly what stage of the test has been reached. The wipers of the control switch are now on the third set of contacts and in this posi tion a circuit is completed for relay TH (Fig. 8) from earth over conductor 67, which, it will be remembered, is earthed during the routine cycle over armature 6d of relay DB, wiper 68 of the sender control switch CS and bank contact 3, conductor 121 (Figs. 3, 5, 7 and 8), winding of relay; TH to battery. Relay TH opcrates and at armature 136 completesthe following high resistance loop across the incoming leads to the repeater being dealt with: conductor 122 (Fig. 2), bank contact and wiper 123 of secondary distributor SD, first bank contact .and wiper 121 of primary distributor PD conductor 125, back contact and armature 126, conductor 127 (Figs. 1, 6 and 5), armature 128 and back contact, conductor 129 (Figs. 5, 7 and 8), armature 130 and back contact, conductor 131 (Figs. 8,7, 5,3 and 1) armature 132 and back contact, conductor 133 (Figs. {1, 3, 5 and 7) right hand Winding of relay TF, conductor 134;, resistance 1 16, conductor 13%, resistance135, front contact andarmature 136, conductor 137, springs controlled by armature 138, resistance 139, conductor 140 (Figs. 7, 8, 6 and 1) armature 14:1 and back contact, conductor 142, wiper 1 13 and first bank contact of PD, wiper 144 and bank contact of SD, conductor M5 and from thence to the repeater being dealt with.

The combination of resistances thus connected across the calling loop is 01 sucha value that if the impulse accepting relay of the repeater is in correct adjustment it. will not operate. If the-relay is too lightly tensioned however, it will operate at this. period and reverse the'current direction in 5 the calling loop thereby causing the polarized relay TF to operate and close the circuit to relay NOT (Fig. '8) as follows: earth, armature 1 17, conductor 1418, armature 14:9 and back contact, winding olire- 12o lay NOT to battery. The operation ofrelay NOT disconnects the operating circuit 01": relay ATH at armature 150, thus pre venting the step'pingof the control switch and stops any further routining.

Assuming that the impulse accepting relay is in correct adjustment, relays TF and NOT will not be operated and routining will continue. Earth at armature 151 of relay DB, which it will be remembered is 130 DM to battery.

pulsing, is extended over conductor 156,

;relay TV, armature 153 and front contact,

armature 154 and back contact, upper winding of relay TV'to battery, whereupon the relay operates all its armatures. Onthe next pulse a circuit is completed as follows: earth, armature 151, conductor 156, armature 152, and front contact, armature 242 and front contact, armature 401 and back contact, armature 150 and back contact, upper winding of relay ATH to battery. Relay-AT H operates its light armature 402 and at the end of the pulse operates completely in the following circuit: battery, upper winding of-relay ATE, armature 150 andback contact, lower windin of'relay ATH, armature 402 and front contact, conductor 67, key 66, conductor 65, front contact and armature'64, conductor63, springs controlled by armature 62 to earth. Relay ATHope ns the circuit of relay TV at armature 154, and at armature 157 completes a circuit formagnet-DM as follows: earth, armature 156, armature 157, conductor 177, third bank contact and wiper 72, interrupter springs 73, winding of magnet Magnet DM" energizes and opens springs 73 thereby breaking its own circuit, the magnet then de-energizes and the wipers 118, 68, 72 and 3-26 are stepped onto the fourth set of contacts.

. Relay TH is released when the wipers of the control switch move off the third set ofcontacts, and earth is extended from armature 158 over conductor 159 to-the fourth contact on which wiper 72 is now resting. Magnet DM again operates and which it will=be remembered are in series with the calling loop to the repeater; the resultant resistance'which is now across the loop is of such avalue thatthe impulse accepting relay should operate.

Assuming that the impulse accepting relay in the repeater now operates, the resultant reversal of current in the loop will cause polarized relay TF to operate and complete a circuit as follows: earth, armature 147, conductor 148, armature 149 and front contact, conductor 161 (Figs. 8, 6 and 5), back contact and armature 162, winding of relay OT to battery; relay OT operates and locks to earth in the following circuit: battery, winding of relay OT, armature 162 and back contact, armature 403 and front tact, conductor 164, armature 165, conductor 166, upper winding of relay OL to battery; thus the relay OL operates its light armature 167. At the completion of the pulse, relay OL will operate fully in the following circuit: earth, armature 167, lower winding of relay-0L, conductor 164, armature 165 and front contact, conductor 166, upper winding of relay OL to battery. On the commencement of the next pulse from relay DR the driving magnet DM of the control switch is energized in the following circuit: earth, armature 151, conductor 156, armature 163 and front contact, conductor 168 (Figs. 8, 7, 5 and 3), winding of DH to battery, so that at the completion of the pulse the wipers of the controlswitch will be moved on to the sixth set of bank contacts. In this position earth is extended from wiper 68 over conductor 169 to relay OTC which operates and I locks operated in the following circuit: battery, winding of relay OTC, armature 405, conductor 117 (Figs. 5 and '7), armature 107 and back contact to earth on conductor 67. At armature 406, relay OTC short-circuits resistance 146 from the calling loop to the repeater. Relay OT is released at armature 162 and it again completes the loop to the repeater at armature 128, thereby causing the associated rotary switch to hunt for an idle coder; a reversed battery condition is placed on the calling loop during hunting. Relay TF. which is of the shunt field polarized type will be operated from the reversal thus extending earth from armature 147, conductor 148, front contact and armature 170, conductor 171, armature 172 and back contact, conductor 173, armature 174 and back: contact, conductor 175, lower winding offtwo-step relay TM to battery, whereupon relay TM will operate .its light armature 176. It will be remembered that during this period the coder finder is hunting, and as soon as a free coder is found the relevant switching relay will be operated thereby re- ?toring normal current flow in the calling Relay TF will release during this condition thereby allowing two-step relay TM to operate completely and lock in the following circuit: battery, lower winding of relay TM, conductor 175, back contact and armature 174, conductor 173, upper winding of relay TM, armature 176 and front contact, armature 107 and back contact and thence to earth on conductor 67. Atarinature 17 8 a circuit is completed for magnet Dlvl as follows: earth, armature 156 (Fig. 8),armature 157 and front contact, conductor 177, armature 178 and front contact, conductor 179, 6th bank contact and wiper 72, interrupter springs 73, winding of- DM to battery; the wipers are accordingly stepped onto the seventh set of contacts whereupon relay TD operates over the following circuit: earth on wiper 68, seventh bankcontact, conductor 180, winding of relay TD to battery. Relay TD in operating completes the following circuit: earth, resistance 181, winding of relay TE (Fig. 7 conductor 182, front contact and armature. 183, back contact and armature 184, conductor 185 (Figs. 5, 7, 9 and 10), resting springs of keys 186 and 187, conductor'188 (Figs. 10, 8, 6 and 4), armature 189, conductor 190, wiper 191 and first bank contact of P13 wiper 192 and bank contact of SD, to battery over the outgoing negative junction via. conductor 193. Relay TE operates and closes the following circuit: battery, winding of relay ATE and front contact, armature 194, conductor 267 (Figs. 7, 8 and 10), resting springs of keys 196 and 197, conductor 198 (Figs. 10, 8, 6 and 4), armature 199, conductor 200, wiper 201 and first bank contact of PD wiper 202 and first bank contact,

over conductor 203 to earth over the positive junction outgoing to the distant call indicator 066%. It will be appreciated therefore that relay TE can only operate if the outgoing negative junction is connected to battery and that relayATE can only operate if relay Tlil has operated and if the outgoing positive junction is connected to earth, that is to.

say, relay ATE can only operate if the outgoing junction lines are continuous and not reversed. Relay ATE in operating, connects earth at armature 204, over coni ductor 205 to step the control switch CS to its 8th position. A circuit is then completed as follows: earth on wiper 68, eighth bank contact, conductor 206, armature 207 and back contact, winding of relay TN to battery, whereupon relay TN will operate and lock operated in the following circuit: battery, winding of relay TN, armature 208 and front contact, conductor 117 (Figs. 4, 3, 5 and 7 armature 107 and back contact and thence to earth on conductor 67. The operationof relay TN puts the impulsing group of relays into operation, this grou comprising relays CC, SC, SW SZ, (Fig. 9), and E, F,'G, and H 4).

7 Upon operating relay TN closes the following circuit: earth on wiper 68, eighth bank contact, conduct-or 206, armature 207 and front contact, conductor 209 (Figs. 4, 6, 8, 10 and 9), interrupter springs 210, armature 211 and back contact, armature 213 and back contact, upper winding of twostep relay CC to battery, thus causing the relay to operate its light armature 212. It will be noticed thatwheii.relay TM operated its armature 138 (Fig.7) alloopwas placed across the calling leads to the repeater by way ofwipers and bank contacts of secondary and primary distributors, conductor 125, back contact and armature 126,

conductor 127 (Figs. 4, 6, and 5), armature 128and back contact, conductor 129 (Figs- 5,

7 and 8), armature 130, conductor 131, con- 1 ductor 214 (Fig. 7), armature 215 and back:

contact, conductor 216, springs controlled by armature 217 (Fig. 5), conductor 218, armature 318, resistance 139, conductor 140, armature 141 and back contact, conductor 142, via' wipers and bank contacts of primary and secondary distributors to the repea-ter. As previously mentioned, the first effective pulse from interrupter springs 210 causes relay CC to operate its light armature 212, at the completion of the pulse the relay operates fully in the following circuit: bat-' tery, upper winding of relay CG, back contact and armature 213, lower winding of CC, front contact and armature 212,

conductor 209, front contact and armature 207, conductor 206, to earth on wiper 68, thereby extending an earth 21 to operate relay SW.

' It must be mentioned here that although pulsing springs 210 and 220, are operating at the same speedconveniently in this case 10 per second, they are arranged to beout ofphase with each other i. e. when 210 is closed 220 is open, and it'will be readily understood when relay SW breaks its armature 215, the calling loop to the repeater will still be maintained via the now made pulsing spring 220. On the reception of the next pulse from springs 210, earth will be connected over arniatures 211 and 221 to the lower winding of relay SC, causing the relay to operate its light armature222,and it will be appreciated from the foregoing that interrupter springs 220 will 'now' be open, thereby transmitting one impulse to the 1111-" pulse accepting relayof the repeater under test, which in turn transmits the impulse to the coder in use. At the cessation of the second pulsefrom springs 210, relay SC will fully operate over both windings in series and will lock up via arinatures 223 and 222,

its armature I will 1be-transmitted tothe coder and-that furthermore, the two-step. relays E, F, G and H' (Fig. 4) will be operated in turn first partially and then completely by earth extended over conductor 225, at each make and break of armature 224 of relay CC.

hen two step relay-H operates after the four digit number 1111 has been transmitted into the coder, it extends earth via its armature 226 over conductor 227, so that t is control switch CS will be stepped forward onto the ninth set of contacts and a circuit prepared for the reception of the coded pulses. It will be noticed that during the foregoing operations relay TN operated TJ at armature 228, so that earth is connected up over the followingcircuit: earth, front contact and armature 229, armature 230' and back contact, conductor 231, wiper 232 and bank contact of' primary distributor PD conductor 366, wiper 365 and first bank contact of secondary distributor SD; and causes the switching relay HA in the repeater under test to be short-circuited and released, thereby disconnecting the outgoing junction to the call indicator-office, so that no equipment shall beoperated thereat. Immediately the coder has received its full complement of digits, it will accordingly translate and commence-to send out the code over the junction leads, which have been imitated in the routiner. The-code for digitone, includes one so-called positive pulse which consists I of current How in such a direction as to operate, the posltlve polarized relay LP which was connected across the outgoing leads by'relay TJ. This circuit may be traced as follows: WViper 192 of secondary distributor SD,first bank contact and wiper 191 of primary distributor PD conductor 190, back contact and armature-189, conductor 188, resting springs of keys 187 and 186, conductor 185 (Fig. 10), armature 184 and back contact, conductor 233 (Figs. 5, 6, and 4), armature 234 and front contact, conductor 235 (Figs. 4, 6 and 8) winding of positive polarized relay LP, conductor 267 (Figs. 8 and 10), resting springs of keys 196 and 197, conductor 198, armature 199 and back contact, conductor 200, wiper 201'and first bank contact of primary distributor PD wiper 202 of secondary distributor SD. Positive polarized relay LP will thus operate four times corresponding to the positive pulse in each of the re-transmitted digits 1111. 'At each operation LP closes its armature 237 thereby extending the earth from wiper 68 and ninth bank contact of the control switch CS, over conductor 236 (Figs. 3,5, 7 and 8), front contact and armature 237 conductor 168, winding of magnet DM to battery, causing the wipers to be moved onto the next set'of contacts. It will be noticed that contacts 9, 10, 11 and 12 of the control switch bank associated with wiper 68' are connected together, so as'to'maintain earth on armature 2370f relay LP- while the switch "is passing over these positions,

and the correct reception of all four of the the control switch CS, causing the wipers to move to the 14th position. At this period the routiner is so arranged to test the private guard on release feature of the repeater under test, so that-when relay TR operates its armature 241, the following sequence ofoperations will commence. Pulsing earth at:

armature-151 of relay DR is extended overconductor 156,-armature 152 and back'contact, armature 241 and front contact, upper winding of relay TV to battery, thus causing the relay to operate its'lighbarmature 155, and at the completion of the pulse the relay will operate all its armatures over both windings connected in series in the following circuit: battery, upper winding of relay, TV, front contact and armature 241, lower windingof relay vTV, front contact and armature 155 toearth. On the commencement of the next pulse, earth will be extended over the now operated armature 152, armature 242 and back contact, winding-of relay TWV to battery; relay TWV operates and completes a circuit for relay TX as follows: earth, armature 239 and front contact, front contact and armature-243, conductor 244, armature 245 and back contact, conductor 246, armature 247 and backcontact, conductor 248, upper winding of twostep relay TX to battery.

Relay TX operatesits light armature'249 over the circuit described, and at the-completion ofythe pulse after relay vTV has'released it operatesall its armatures over the following circuit: battery, vupper winding ofrelay TX, conductor 248, back contact and armature 247, conductor 246, lower winding of' relay TX, front" contact and armature 249, conductor 240 (Figs. 7 5, 6 and 8), front contact and armature 239, to earth. At this stage of the test the private guarding earth from the repeater is extended from wiper 112 of the secondary distributor SD, conductor 111,-first bank contact and wiper 110 of primarydistributor PD conductor 409, back-contact and armature 113, conductor 109 (Figs. 4, 6, 8 and 7), armature 108 and back contact, armature 116, armature 115 and front contact, conductor 250, armature251 and back closes a locking circuit as follows: battery,

winding of relays TY and ATY in parallel, front contait and armature 253, front contact an armature 115, back contact and armature 116, back contact and armature 118.connctor 109, and thence to guarding :1 1. at repeater.

of relay re Ly Til again operates and closes a lOCLlllg' circuit for itself as follows: battery, winding of relay TVV, conductor 408, front contact and armature 2 15, conductor 2-l-i, armature and front contact,

front contact and armature 239 to earth. Relay TW upon operating closes a point in the circuit of relay GB at armature 258, opens the initial energizing circuit of relays TY and ATY at armature 251 and opens the calling loop to the repeater at armature 130 whereupon the repeater will commence to release. When the guard relay of the repeater under test has released consequent on the disconnection of the impulse accepting relay, a high resistance relay is connected in series with the private lead, and although the high resistance relay is energized in this circuit the reduction of current in the circuit causes relays TY and ATY to release. immediately armature 253 of relay leaves its front contact the circuit of said high resistance relay in the repeater will be broken and it will thereupon release and again extend a full earth over the private lead. At this period however, relay TVV is being held operated and hence relay ATY will remain (la-energized. Earth is now eX- tended from the private lead over conductor 109, armature 11.08 and back contact, armature 116 and back contact, armature 115 and front contact, armature 253 and back contact, armature 4-07 and back contact, winding of relay TZ to battery. Relay TZ operates over this circuit and closes the following circuit: earth, armature 254C. and front contact, conductor 260 Figs '7, 5 and 3), 14th bank contact and wiper 72, interrupter springs 73, winding of magnet DM to battery. The wipers of the control switch are thereby stepped onto the 15th set of contacts. f

It will be appreciated from the'foregoing, that the test imposed on the repeater at this period guarding earth, a complete opening of the :alling loop, high resistanceeartli perlod, and then a re-guarding earth when all preceding switches have released. If, however, the repeater fails to comply with any one the above conditions, relay GR will be operated over the following circuit: earth, arma ure and back contact of relay TZ, armature and back contact, front contact and armature 256, conductor 257, front On the next pulse consists of the reception of a contact and armature. 258, conductor 259, winding of relay GR to battery; relay GR operates in this circuit and extends earth over armature 116and conductor 109 to guard the repeater and enable the fault to be located. i

in the course of a successful test the circuit of relay GR is completed when relay ATY releases after relay TW has locked operated, i. e. when the inclusion of the high resistance relay in the circuit of relay ATY has caused relay ATY to release and close armature 255, whereas the circuit of relay TZ is not completed until the high resistance relay has released due to its circuit being opened by the release of rela TY, and hence it is essentialthat relay GR shall be slow to operate,to enable the fast operating relay TZ to energize first and open the circuit of relay GR at armature 25d and allow the routine cycle to continue.

Two'further pulses are then sent to magnet DM over the following circuit-z earth, armature 251 and front contact, conductor 260 (Figs/7, 8 and6), armature 261 of pulsing relay DR, conductor 168, winding of driving magnet 'DM to battery, thereby causing the wipers of the control switch to be moved into the 17th position. When the wipers of the control switch move into the 17th position thecircuit of slow-releasing relay TR over conductor 238 is opened, and the earth on wiper 68 is now extended over the 17th'contact, conductor 262, winding of relay TG tobattery. RelayTG operates over the circuit described and locks up in the following circuit: batter, winding of relay TG, armature 263 and front contact, conductor 117 (Figs. 5 and 7), armature. 107 and back contact and thence to earth over conductor 67 Relay TGr extends battery and earth via the windings of relay B (Fig. 9) to operate the switching relay in the repeater under test. The earth may be traced as follows: earth, resistance 276, key 275, key 274, lower winding of relay R, conductor 273 (Figs. 9, 7 and 1), back contact and armature 272, armature 271 and back contact, armature 268 and front con tact, conductor 267 (Figs. 5, 7, 8 and 10), key 196, key 197, conductor 198, armature 199 and back contact, conductor 200, primary and secondary distributors to the positive outgoing junction. The battery may be traced as follows: battery, resistance 277, key 278, key 279, upper winding of relay R, conductor 280 (Figs. 9, 7 and 8), back con tact and armature 281, conductor 282 (Figs. 8, 7 and 5), armature 283 and back contact,

front contactand armature 1842, conductor 185 (Figs. 5, 7, 9 and 10), key 186, key 187, conductor 188 (Figs. 10, 8, 6 and 4:), armature 189 and back contact, conductor 190, primary and secondary distributors to the negative outgoing junction. During the operation of relay TG, relay TR was holding due to the retaining effect of the copper slug on its core, however, when the magnetic flux finally subsides, relay TR will release. It will be remembered that the holding circuit for relay TX extended from armature 239 over conductor 240 and that the holding circuit for relay TlV extended from armature 239 over conductor 244, hence when armature 239 opens the relays TX and T9 will release, the locking circuit of relay TV is opened at armature 241 and relay TZ will finally release due to its disconnection at armature 115 of relay TX.

A circuit may now be traced for stepping the control switch as follows: earth, armature 264 of relay TlV, conductor 265 (Figs. 8, 7, 5 and 3), 17th bank contact and wiper 72, interrupter springs 7 3, winding of magnet DM to battery, so that the wipers will now be moved into the 18th position, where earth is extended via wiper 68, conductor 266, winding of relay TK to battery.

Relay TK operates and locks up in the following circuit: battery, winding of relay TK, armature 269 and front contact, arma ture 270 and back'contact, conductor 117, armature 107 and back contact and thence to earth on conductor 67. At armatures 271 and 283 relay TK reverses battery over the junction to imitate the distant call indicator operator answering. The circuit may be traced from, the negative outgoing junction 193, secondary and primary distributors, conductor 190, back contact and armature 189, conductor 188, resting springs of keys 187 and 186 (Fig. 10), conductor 185, armatures 184, 271 and 272, conductor 273, lower winding of relay B (Fig. 9) resting springs of 274- and 27 5through resistance 276 to earth; and following the other part of the circuit; battery via resistance 277 (Fig. 9), resting springs of keys 278 and 279, upper winding of relay R, conductor 280, armature 281 (Fig. 8), conductor 282, armatures 283 and 268 (Fig. 5), conductor 267, resting springs of keys 196 and 197, conductor 198, armature 199, conductor 200, wiper 201 and first bank contact of primary distributor PD to wiper 202 of secondary distributor SD and positive outgoing junction 203. The above current reversal causes the polarized relay in the repeater to operate, and consequently, battery and earth connections from the impulse accepting relay are reversed to the shunt field polarized relay TF in the routiner by way of earth via winding of impulse accepting relay in the repeater, (conductor 122) first bank contact and wiper 123 of secondary distributor SD, first bank contact and wiper 124 of PD conductor 125, armature 126, conductor 127, armature 128 (Fig. 5), conductor 129, armatures 130 and 284- in parallel, conductor 131, winding of relay TL, righthand winding of relay TF, conductor 134, armature 217 conductor 218, armature 138, resistance 139 (which is approximately equivalent to the maximum junction resistance), conductor 140, armature 141 (Fig. 4), conductor 142, wiper 143 and first bank contact of primary distributor PD wiper 144 and first bank contact of secondary distributor SD, to battery via the other winding of the impulse accepting relay in the repeater. Relay TF operates over the circuit described and completes a circuit for magnet DM as follows: earth, armature 147, conductor 148, front contact and armature 170, conductor 171, armature 172 and front contact, conductor 285, 18th bank contact and wiper 72 of the control switch CS, interrupter springs 73, winding of magnet IBM to battery, thereby causing the switch CS to move its wipers on to position 19, thus proving that the battery reversal from the repeater has been received. In the 19th position of the control switch CS, earth on wiper 68 is connected over conductor 286, winding of relay HG, resistance 410 to battery. Relay HG operates and locks up in the following circuit: battery, resistance 410, winding of rela HG, armature 237, conductor 117, armature 107 and back con tact to earth on conductor 67 One of the. functions of relay HG is to extend interrupted ringing current from. conductor via condenser 411, armature 289 and front contact, armature 290 and front contact, conductor 291, armature 292 and back contact, conductor 273 (Figs. 7 and 5), armatures 272, 271 and 184, conductor 185 Figs. 5, 7, 9 and 10), keys 186 and 187, conductor 188, armature 189 and back contact, conductor 190, primary and secondary distributors to negative outgoing junction 193. If the circuit through the talking condenser of the repeater is closed, ringing current will flow back to the routiner via conductor 122. bank contact and wiper 123, bank contact and wiper 124- of primary distributor PD, conductor 125, armature 128, back contact and armature 126, conductor 127 and back contact, conductor 129, armature 284 and back contact, back contact and armature 293, conductor 294, front contact and armature 295, front contact and armature 296, condenser 412, winding of relay HF to earth. Relay HF is energized over this circuit and at its armature 297 extends earth over conductor 298, winding of relay AR to battery, so that relay AR operates and shunts its winding by a resistance 413, thereby rendering its slow-to-release to enable it to hold up during the pulsating earth from relay HF. When relay HG operated, the pulsing earth at armature 151. of relay DR (Fig. 6) was extended over conductor 301, armature 300 and back contact, armature 299 and front contact, lower

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