US2073752A - Telephone system - Google Patents

Description

March 16, 1937. J. E. NORTON I 2,073,752

TELEPHONE SYSTEM Filed March 25, 1936 4 Sheets-Sheet 1 JJIJJO 770N717 01 T mad/HAL OFF/CE V FIG.

POLAR/ZED FIG 3 FIG. 4

FIG. 5

FIG

FIG. 2

INVENTOR J. E. NORTON March 16, 1937. J. E. NORTON TELEPHONE SYSTEM 4 Sheets-Sheet 2 Filed March 25, 1936 SE81 QEEQQQ L $9 6 N 6R lAl VVVVV INVENTOR J. .E NORTON 8;

FIG. 3

March 16, 1937. J. E. NORTON 2,073,752 h TELEPHONE SYSTEM.

Filed March 25, 1936 4 Sheets-Sheet 3 OT-Z OFF/CE r ATTORNEY March 16, 1937. J. NORTON 2,U73, 752

TELEPHONE SYSTEM Filed March 25, 1956 4 Sheets-Sheet 4 1 W 8 & jg u E I L: Q I F Q "a Hf I UHJQLA INVENTOR J ENORTON A T TOR/VEV Patented 'Marr 16, 1937 PATENT OFFICE TELEPHONE SYSTEM John Ernest Norton, Detroit, Mich., assignor to American Telephone and Telegraph Company, a corporation of New York Application March 25, 1936, Serial No. 70,865

6 Claims.

This invention relates to telephone systems and particularly to semi-automatic telephone systems.

It is the object of the invention to facilitate the completion of calls through a manual tandem switchboard to subscribers lines in an automatic ofiice.

In multi-oi'lice telephone systems it may be too expensive to provide direct trunks between each office and all of the other offices, in which case a tandem ofiice is provided to concentrate the interoffice trafiic. In systems which include a manual tandem office and an automatic local office, it is'usual to provide a cordless B board in the automatic oflice for completing calls incoming from the tandem or other manual ofiices. According to this invention, operators keyset and control apparatus and one or more register senders are provided in the tandem ofiice in place of providing a cordless B board in the automatic office. Upon answer of an incoming call by the tandem operator an extension of the incoming trunk to an idle trunk outgoing to the automatic office, an idle register sender is automatically connected to the seized outgoing trunk and by operation of the numerical keys at the operators position, the called number is registered and the register sender is thereupon effective to control an incoming selector and a final selector in the automatic office to complete connection with the called subscribers line. A feature of the invention is the provision of relay means for holding the line relay of the incoming trunk after the keying of the called number is completed until 35 the sender is dismissed.

The invention will be more readily understood by considering a telephone system in which the invention is embodied. One such system is illustrated schematically in the drawings which form 40 a part of this specification. The invention is, of course, not limited in its application to the particular system shown in the drawings but may be applied to any system in which an intermediate manual operator is provided with key-set 45 equipment for use in completing calls to automatic offices.

Referring to the drawings,

Figure 1 represents a subscribers station A, a cord C, and an outgoing trunk circuit OT-l 50 all of which are in a manual oflice X; Fig. 1 also shows an incoming trunk circuit IT in a manual tandem oilice Y;

Fig. 2 represents an operators position comprising telephone, key-set, and associated con 55 trol equipment in the tandem oflice Y; I

Fig. 3 represents an outgoing trunk circuit OT-2 in the tandem ofiice Y and also an incoming selector IS, final selector FS, and called subscribers station B'in an automatic oflice Z;

Fig. 4 represents a portion of a register sender in the tandem office Y which sender is operatively connected by a link with the trunk circuit OT-2 of Fig. 3; and

Fig. 5 shows the position in which Figs. 1 to 4, inclusive, should be placed to form an operative system.

The oflice X is a manual common battery of fice, the cord C being one of the cords at an A operators position for use in answering calls and extending calling lines to idle outgoing trunks. The outgoing trunk equipment OT-l associated with trunk Tl extending to the tandem office Y provides for repeating coil transmission of Voice currents and polarized supervisory signaling over trunk Tl the usual high-low supervisory relay being bridged across the tip and ring conductors of the cord.

The incoming trunk equipment IT in tandem oflice Y is a modification of the incoming trunk disclosed in Fig. 1 of Patent 1,629,099, granted to C. B. Fowler May 17, 1927; the modification enables the use of key-set pulsing equipment in extending calls to automatic offices. The relays 29 and of trunk equipment IT and the corresponding relays for other incoming trunks constitute a sequence control whereby the tandem operators position and telephone equipment is connected to the incoming trunks in succession in the manner disclosed in the aforementioned Fowler patent. The key-set and associated control apparatus provided at the tandem operators position is substantially the same as that disclosed and described in Patent 1,780,906, issued to Carpenter et al. November 11, 1930. The link and register sender equipments in the tandem office are similar to those disclosed in Figs. 4, 5, 6 and 7 of the aforementioned Carpenter et a1. patent and reference thereto may be had for a detailed description of the operation of these equipments. Only so much of a link and a register sender are shown in the drawings as is required for a clear and complete description of the present invention; the reference characters applied to the various elements shown are the same as the reference characters applied to these elements in the aforementioned Carpenter et a1. patent. The switches IS and F5 in ofiice Z are of the panel type adapted for revertive control by a register sender; reference may be had to Patent No. 1,658,829, issued to C. H. Berry, February 14, 1928 for a description of the operation of the incoming and final selector switches.

Upon origination of a call at a station A and answer of the call by an operator in office X in 5 well-known manner, the line H is extended through jack l2, cord C, and jack IE to the outgoing trunk circuit OT-| and thence over the interofiice trunk TI to the incoming trunk circuit IT in the tandem office Y. Operation of the line relay 2| of equipment IT effects the automatic extension of the call to the tandem operators telephone set; and, upon the called office name and line number being received from the 'A operator in office X, the tandem operator inserts the plug 25 of equipment IT in a jack connected to an idle trunk leading to the called ofiice. If the called line is in an automatic oflice, an idle register sender is thereupon automatically associated with the outgoing trunk equipment OT2. The operator also depresses the position key KP to operatively associate the position keyset and associated control apparatus with the trunk equipment IT and operates the non-locking numerical keys corresponding to the digits of the called subscribers number. The number of the called station is thus registered in the associated register sender. Upon completion of keying, the key-set and key control apparatus are disconnected from the trunk equipment IT and the conductors of the incoming trunk IT are cut through to the outgoing trunk equipment OT, so that the line relay 2| of equipment IT will be held operated until the register sender is dismissed. Upon registration of the keyed numher, the register sender proceeds to control, over the trunk T2, the setting of the incoming selector IS and final selector F8 in the called office. Upon completion of the setting of these switches, the register sender is disconnected from the out- 10 going trunk equipment OT-2 and the connection is cut through to the conductors of trunk T2 so that the line relay 2| of equipment IT is held operated over trunk T2 in series with the calling supervisory relay 2il| of the incoming selector IS. Upon answer of the called subscriber the current over trunks T2 and T! is reversed to cause the operation of the polarized supervisory relay IS in the outgoing trunk equipment OT-| in office X and operation of the supervisory relay l3 in cord C. When the cord C is disconnected from trunk equipment OT|, relay 2| of trunk equipment IT and the supervisory relay of the incoming selector IS release; the tandem operator receives a disconnect signal and the switches IS and F8 are returned to normal in usual manner. When the tandem operator disconnects trunk equipment IT from the trunk equipment OT-2, these equipments are completely restored to normal.

A detailed description of the portion of the system directly relating to the application of this invention follows:

When the operator in ofiice X inserts the plug of a cord C in jack l5, relay l6 operates in an ob- 5 vious circuit, and supervisory lamp I4 is lighted.

Relay l6 causes the operation of relay I1 and relay l1 closes a circuit for operating relay 2| in trunk equipment IT of tandem oflice Y. This circuit is traced from battery at the inner lower back contact of relay 22, through the lower winding of relay 2|, lower conductor of trunk T| front contact of relay I'i, lower right winding of repeating coil l8, winding of polarized relay l9, upper right winding of repeating coil 8, upper conductor of trunk TI, upper winding of relay 2|,

to ground at the upper back contact of relay 22. The current in this circuit is inefiective to operate polarized relay |9. Relay 2| closes an obvious circuit for operating relay 28 and a circuit, for lighting the trunk guard lamp, from battery through the lamp, resistor 26, lowermost back contact of relay 22, lower back contact of relay 23, to ground at the front contact of relay 2|. Relay 28 closes at its upper front contact a circuit for operating the start relay 29. Relays 29 and 30 of trunk equipment IT and the corresponding relays of the other trunks in the group constitute a sequence control whereby the operators telephone is automatically connected to one waiting trunk at a time in the order in which the trunks are numbered. As shown in the drawings the trunk equipment IT is the last in the group. For a complete description of the operation of the sequence control, reference may be had to the aforementioned Fowler Patent 1,629,099. Assuming the operator to be idle at the time trunk TI is seized and relay 29 operates, a circuit is closed from battery through the winding of relay 30, front contact of relay 29 and back contacts of the corresponding sequence relays of each of the other trunks in the group, to ground at the operators position. Relay 33 is operated by the current in this circuit. At its lower front contacts, relay 30 connects the conductors of trunk Tl, over conductors 3| and 32, to the operators position equipment; and at its inner upper front contact connects the guard lamp and resistor 26, over conductor 33, through the winding of pilot relay 38, to the winding of relay so. Relays 38 and 4E! operate; the operation of relay 38 lights the position pilot lamp, and the operation of relay 48 causes the successive operation of relays 4| and 42. The operation of relay 32 short-circuits the Winding of relay :30 thereby shunting and extinguishing the trunk guard lamp. The release of relay 40 causes the release of relays 6| and 32 and the release of relay 42 opens the short circuit around the winding of relay 4%. Relays 4i), 4| and 42 are thus successively operated and released to flash the trunk guard lamp to indicate to the operator the particular one of the trunks to which her telephone set is connected. The aforementioned operation of relay 3! also closes a circuit from battery through the lower front contact of relay 28, lower winding and inner back contact of relay 2?, uppermost front contact of relay 30, over conductor 34 to the operators position, and through windings of relays 43 and 3 to ground. The current in this circuit is ineffective to operate relays 2'! and 43, both of these relays being marginal; but relay &4 is operated and closes a circuit for operating a group of tone control relays, relay 45 being the first and relay G6 the last relay of this group. The operation of relay 45, and the succeeding relays (not shown) of this group, causes the transmission of three impulses of tone current from the tone source 3'! through the back contacts of relay 46, over conductors 3| and 32, and over trunk Tl, through repeating coil H! of trunk equipment OT-| to the operator in ofiice X. The operation of relay 56 at the end of the last of the three impulses completes a connection between the operator in office X and the operator in tandem oihce Y. The tone having ceased, the operator in office X passes the ofice name to the tandem operator. The tandem operator thereupon inserts the plug 25 in an idle jack in the group connected to trunks leading to the called oifice. The jack 89 represents a group connected to trunks leading to a manual ofice,

trunk jack, through the tip of plug 25, inner'upper back contact of relay 24, conductor 35, back contact of relay 99 of the operators key control apparatus, back contact of relay 48, through the busy-test coil 5910f the operators telephone set. If plug 25 is inserted in jack 99, a circuit is also closed from battery through both windings of relay 48 in the operators position equipment, over conductor 31, lower back contact and winding of relay 24 of trunk equipment IT, sleeve conductors of plug 25 and jack 89 to ground. The current in this circuit is effective to operate relay 48 but ineffective to operate the marginal relay 24. Relay 48 opens the busy-test circuit and connects the winding of relay 49 across the tip and ring of the plug 25 so that when the plug is fully seated relay 49 may operate in a series circuit over the tip and ring conductors of the seized outgoing trunk. Relay 49, operated, short-circuits the high resistance lower winding of relay 48, thereby causing the operation of sleeve relay 24. Relay .24 then locks over the sleeve, causes the release of relays 4B and 49, and closes a circuit for operating relays 22 and 21. This circuit is traced from battery through the lower front contacts of relay 24, upper winding of relay 2'! in parallel with the winding of relay 22, to ground at the upper back contact of relay 23. At its inner front contacts, relay 22completes the connection from trunk TI, through the windings of relay 2| in parallel with condensers 29, to the tip and ring conductors of plug 25. The operation of relay 22 also extinguishes the guard lamp of trunk IT and the operation of relay 2! causes the release of relay 29. Relays 2| and 28 remain operated until the connection is released. When cord C is disconnected from jack I5 in oflice X, the release of relay I! in outgoing trunk equipment OTI causes the release of relays 2I and 28. The release of relay 28 closes the circuit for operating the disconnect signal relay 23. Relay 23 locks through its inner upper front contact, causes the release of relays 22 and 21, and lights the guard lamp as a disconnect signal. When the tandem operator removes the plug 25 from jack 89, relays 24 and 23 release in succession, thus restoring the trunk equipment IT to normal.

If the called oflice is a panel ofiice, and the plug 25 is connected to jack BI the circuit for operating relay 48 of the operators position equipment is traced from battery through the windings of this relay, conductor 31, lower back contact and winding of sleeve relay 24, sleeve conductors of plug 25 and jack 8|, upper back contact of relay 84 of trunk equipment OT2, winding of relay 85, and winding of relay 86 to ground. Relays 48 and 85 are operated by the current in this circuit but relays 24 and 86 are marginal and do not operate at this time. Relay 48 opens the busy test path and connects the winding of relay 49 to the tip and ring of the plug 25 but relay 49 is not perated. Relay 85 closes an obvious circuit for operating relay 8! and relay 8! closes a circuit from ground at the inner lower back contact of relay 83, through the lower back contact of relay 88, lowermost front contact of relay 81, over conductor I99 to operate group relay 499 and thereby initiate the operation of an idle link to efiect connection of an idle register sender with the trunk equipment OT--2, as described in detail in the aforementioned Carpenter et al. patent. When the trunk-hunting switch (not shown) of the link engages the terminals to which the conductors I9I, I92,'I93, I94, I95. and I96 are connected a circuit is closed from battery through the winding of relay 89, inner lower front contact of relay 8], upper back contact of relay 88, lowermost back contact of relay 83, over conductor I95, test terminal and test brush of the trunk hunting switch (not shown) through the front contact of relay 525 and the windings of relays 5I I and 592 in the link. The trunk-hunting operation of the link is stopped by relays 592 and 5| I. In operating, relay 89 closes at its lowermost front'contact a holding circuit over conductor I95; and, at its inner lower front contact, a circuit for operating relay 88. Relay 88 locks through its inner upper front contact under the sole control of relay 8?, disconnects ground from conductor I99 to allow group relay 499 to release, and at its upper back contact opens the operating circuit of relay 89. The link completes the connection between the trunk equipment 0T-2 and an idle register sender in the manner set forth in the aforementioned Carpenter et al. patent.

. At the same time as the plug 25 was inserted in jack 8|, the operator in the tandem ofiice depresses the non-locking key KP to effect the association of the numerical key set and control apparatus with the plug 25. Operation of key KP closes a circuit through the winding of relay B5 of the key control apparatus and resistor 65. Relay 66 is operated by the current in this circuit and locks through its lower front contact to ground at the key release key KR. Relay 66 opens the busy test circuit over conductor 39 from the tip of plug 25 and. closes obvious circuits for operating relays 6! and I2. Relay I2 closes a circuit for lighting the key pulsing signal lamp 13, opens the operating circuit of relay 89, and connects ground over conductor 15 to the numerical keys. With relay 6! of the key control apparatus operated, and with a register sender connected to trunk equipment OT2, a circuit is closed from battery through resistor II, the inner lower back contact of relay 68, front contact of relay 61, over conductor 35, uppermost back contact of relay 24 of trunk equipment IT, ring conductors of plug 25 and jack 8|, inner upper back contact of relay 83 of trunk equipment OT2, outer left back contact of relay 99, conductor I92, through the link, conductor 529, inner back contact of relay 895 of the register sender, inner lower back contact and winding of relay 6 I 2, lower back contacts of relays 895, 891 and 898 to ground. .Relay 6I2 of the register sender, operated by the current in this circuit, looks through its inner lower front contact and transfers the connection from conductors I92 and 529, through the windings of relays BIG, M5 and M4 in series to battery. Relay 6I2 also closes a circuit from battery through the windings of relays BII, H8 and 5I9 in series, upper front contact of relay IiI2, uppermost back contact of relay 895, conductor 8"), through the link and over conductor I9I, inner left back contact of relay 99, uppermost back contact ofrelay 83, tip conductors of jack 8! and plug 25, inner upper back contact of relay 24, conductor 39, uppermost front contact of relay 66, continuity contact and winding of relay 19, to ground at the inner upper front contact of relay 65. Relay i9 is operated by the current in this circuit and it locks through resistor II in local circuit. Relay I9 closes a circuit from battery through the winding of relay 68, and from battery through lamp I4 and the lowermost back contact of relay 69, through the lower front contact of relay l9 and inner lower back contact of relay 69, to ground at the inner upper front contact of relay 66. Lamp I4 lights to indicate to the operator that a register sender has been attached to trunk equipment OT-2 and is ready to register the number of the called subscribers line. At its upper front contact, relay 88 completes a connection from the key pulsing conductor 38 to the numerical keys and through the winding of polarized relay 6| to 24 volt battery; at its inner lower front contact, relay 68 completes a connection from the key pulsing conductor 35 to the numerical keys and through the winding of polarized relay 62 to 24 volt battery; and at its lowermost front contact, relay 88 connects 48 volt battery through resistor 55 to the numerical keys.

The aforementioned depression of the KP key was also effective to cause the transmission of two impulses of tone over trunk TI to the A operator in office X in the same manner that three impulses were transmitted; and in response to these two tone impulses, the A operator passes the number of the called line with which connection is desired. Depression of the numerical keys, by the tandem operator, in accordance with the various digits of the called subscribers number is effective in the manner described in the aforementioned Carpenter et al. patent to transmit various combinations of impulses from the key-set over conductors 35 and 36 and conductors |8| and I82 to cause the operation of various combinations of relays 6I4, 6I5 and SIB and relays 8 I1, SIB and GIS in the register sender. These combinations are such as will cause the operation of the one or the other but not both of the polarized relays 6| and 62 at the same time. When the thousands, hundreds, tens and units digits of the called subscribers number have all been registered, relay 885 in the register sender is operated in the manner described in the aforementioned Carpenter et al. patent thereby connecting 48 volt battery through the windings of relays 881 and 888 to conductors I8I and I82 to cause the operation of both of the polarized relays SI and 62 and thereby close a circuit for operating relay 63. Relays 88! and 888, being marginal, are not operated at this time. Relay 63 locks through its lowermost front contact and connects ground through both lower front contacts to the winding of relay BI and conductor 36 thereby increasing the current through the winding of relay 888 in the register sender to cause the operation of relay 888. Relay 888 looks to ground through the upper back contact of relay 88! and causes the release of relay 885, as described in the aforementioned Carpenter et al. patent, thereby causing the release of polarized relay 82 and the operation of relay 64 of the key control apparatus. Relay 64 short-circuits the winding of relay 86 thereby causing the release of relays 88, 81, I8 and I2. The release of relays 88 and 61 disconnects the key-set from conductors 35 and 38 and causes the release of relays 63 and 64.

The aforementioned operation of relay B4 was also effective at its uppermost front contact to connect 24 volt battery to conductor 31 to cause the operation of relay 24 in trunk equipment IT and the operation of the marginal relay 88 in trunk equipment OT-2. At its lower front contacts relay 24 closes its locking circuit over the sleeve conductors of plug 25 and jack 8| and the circuits for operating relays-22 and 21 as hereinbefore described. Relay 21 looks through its lower winding under control of relay 28 and causes the release of relays 29 and 38. The aforementioned operation of marginal relay 86 of trunk equipment OT2 causes the successive operation of relays 82 and 83. Relay 83 connects the upper winding of relay 82 in parallel with the winding of relay 86 to reduce the resistance in the sleeve conductor so that, in case an operator overrides the busy test and inserts the plug of some other incoming trunk into another of the jacks to which the trunk equipment OT2 is connected, the sleeve relay of this other incoming trunk will operate. Relay 83 also disconnects the key pulsing conductors I8I and I82 from jack 8|; and, relay 24 having been operated, completes a circuit for holding the line relay 2| of incoming trunk equipment IT operated, while the register sender is controlling the operations of the incoming and final selector switches in the distant panel oflice. This circuit is traced from battery through resistor 96 and the outer right back contact of relay 98 of trunk equipment OT-Z, lowermost back contact of relay 99, conductor 98, inner upper front contact of relay 83, ring conductors of jack 8| and plug 25, upper front contact of relay 24, uppermost back contact of relay 23, inner lower front contact of relay 22, lower winding of relay 2|, lower conductor of trunk TI, contact of relay I'I, lower right winding of repeating coil I8 of trunk equipment OTI, winding of polarized relay I9, upper right winding of repeating coil I8, upper conductor of trunk TI, upper winding of relay 2|, upper front contacts of relay 22, tip conductors of plug 25 and jack 8|, uppermost front contact of relay 83, conductor 91, inner lower back contact of relay 99, inner right back contact of relay 98, and through resistor 95 to ground. The current in this circuit is effective to hold relay 2| operated but is not effective to operate polarized relay I9 in office X. Over conductors 827 and 53I and conductors I83 and I84, the register-sender controls the operation of the incoming and final selector switches IS and F8 in the distant panel ofiice in the manner described in the aforementioned Carpenter et al. and Berry patents. When final selections have been completed, the operation of relay 684 of the register sender opens the short circuit around the right winding of relay 682 thereby causing the release of relay 525 of the link and the opening of the circuit over conductor I so as to cause the release of relay 89 of trunk equipment OT2. At its uppermost back contact relay 89 connects resistor 92 across conductors I83 and I84 to temporarily hold the supervisory relay 28I of the incoming selector IS operated. Relay 89 also closes a circuit from battery through the winding of relay 99, uppermost front contact of relay 88, inner upper back contact of relay 89, to ground at the inner upper front contact of relay 81. Relay 99 operates, thereby disconnecting conductors 97 and 98 from resistors 95 and 96 and transferring the conductors of trunk T2 from conductors I83 and I84 to conductors 91 and 98 so that relay 28I of the incoming selector IS is now held operated in a circuit which includes the conductors of trunk T2, the windings of relay 2| of trunk equipment IT, the conductors of trunk TI and the winding of the polarized relay I9 of trunk equipment OT--I. The link and register sender are returned to normal, the incoming selector closes a ringing circuit over the called subscribers line and, upon answer at the called subscribers station, the supervisory relay 282 is operated to reverse the connections between the of the calling cord supervisory lamp M in office conductors of trunk T2 and the windings of relay 20 I; The reversal of current over trunks T2 and Ti is effective to cause the operation of polarized relay [9. At its front contact, relay I9 shortcircuits the upper winding of relay I 6 thereby causing the operation of the calling cord supervisory relay i3. Relay l3, extinguishes the lamp M- to indicate to the A operator in office X that the called subscriber has answered. The talking circuit includes the repeating coil of cord C, the repeating coil 88 of trunk equipment OT--l, condensers 26 of trunk equipment IT, and the repeating-coil (not shown) of the incoming selector IS.

When conversation is completed and the A operator disconnects cord C'irom jack l5, relays l6 and El release." The release of relay I'I opens the circuit over'trunks-Tl and T2 thereby-releasing relays l9, =2! and 20!. The release of relay 28! causes the return of selectors IS and FS to normal in usual manner. The release of relay 2i causes the successive release of relay 28, operation of-relay 23, and release of relays 22 and'2l. 'Relay 23 looks under the sole control of relay 2t and 'closesthe circuit for lighting the guard lamp as a disconnect signal. When the tandem operator disconnects plug 25 from jack ill, relays 2t, 85 and ttall release. The release of relay 24 causes the release of relay 23 thereby extinguishing the guard lamp, trunk equipment ITbeing ready for useon another call. The release of relay 85 causes the release of relay 81 and the release of relay 86 causes thesuccessive release of relays 82 and BS. The release of relay 371 causes the release of relays 8% and 9.9, the trunk equipment OT--2 thus being ready for use on another ca1l.-

If the operator in the tandem ofilce Wishes to free her position equipment from an incoming trunk ITto whioh it is connected, the depression of the position release key R is efiective to connect ground to conductor 34 and thus energize the lower winding of relay 2?. Relay 27 operates and locks under the sole control of relay 2B; The operation of relay El causes the release oifrelays L and 38.

If the tandemoperator starts keying the called number before the' register sender is attached, relay (59 operates, locks under control of relay 6B, and connects interrupter 16 to lamp [4 to flash this lamp as a warning signal. If the incoming selector advances to the overflow position, or if the tandem operator fails to key four digits and the incoming or final selector is advanced under the control of the register sender to tell-tale position, the register sender short-circuits both the middle and right windings of relay 602 thereby causing the operation of relay 5% in the link. Relay 52 thereupon connects conductor N36 to a source of interrupted ground potential to cause the alternate release and reoperation of relay 90 of trunk equipment O'I'2. The operation of relay 9t causes the key pulsing conductors 35 and 36 to be disconnected from conductors Ill! and It? and connects the key pulsing conductors through resistors 94 to battery, thereby causing both of the polarized relays 6| and 62 of the key control apparatus to operate and thereby initiate the disconnection of the key set from the trunk equipment IT as heretofore described. With relays 24 and 83 operated, each operation of relay 9!) causes the reversal of current through the winding of polarized relay 19 thereby causing the intermittent short-circuiting of the upper winding of relay It and the consequent flashing X. To correct an eror in keying, the tandem operator may disconnect plug 25 from jack 8| and, if all four digits of the called number have not been keyed, the key release key KR is operated to restore the key control apparatus to normal. Plug 25 is then connected to an idle trunk, the KP key is again operated and the number correctly keyed. If the tandem operator disconnects plug25 from jack 8| prematurely, relays 85, 81 and 88 release. Relay 8'! closes a circuit from ground through the winding of relay 86, upper back contact of relay 81, over conductor H36, through the back contact of relay 524 in the link to battery. Relay 8 operates and connects a busy potential to' the sleeve conductor of 'jack 8| until the sender and link disconnect the ground potential from conductor-185, at which time relay 89 releases; and, when relay 525 operates, the disconnection of battery potential from conductor 886 causes the release'of relay 84, the equipment OT-Z then being normal awaiting use on another call.

What is claimed'is:

1. In a telephonesystem, subscribers lines, a manual oifice, a tandem oifice, an automatic orfice, an operators position equipment in said tandem office, said equipment including a telephone set and a numerical impulse sender, a trunk incoming from said manual oiiioe to said position, a line relay for operation upon seizure of said trunk in the manual oifice, means responsive to the operation of said line relay for confor holdingoperated the line relay of said incoming trunk after disconnection of the incoming trunk from said position equipment, and means effective upon connection of said outgoing trunk with the called line in the automatic office for operatively disconnecting said register controller and for completing a talking connection over said incoming and outgoing trunks.

2. In a multiofiice telephone system, subscribers lines, an operators position comprising a telephone set and a numerical key-set, a plug-ended trunk incoming to said position, an automatic office, a jack-ended trunk outgoing from said position to said automatic office, a line relay for said incoming trunk, means responsive to the operation of said line relay for connecting said incoming trunk to said telephone set, a key, the operation of said key being effective to connect said numerical key-set to said incoming trunk, a register sender for registering the number of a called line upon operation of the corresponding keys of said numerical key-set and for controlling the completion of a connection to the called line in said automatic ofiice, means responsive to the connection of said incoming trunk with said outgoing trunk for connecting said register sender to said outgoing trunk, means assocated with said key-set for indicating to said operator the connection of said register sender and for rendering the numerical key-set operatively effective to control said register sender, means operated upon registration of the required number of digits in said register sender for disconnecting said operators telephone set and key-set from said incoming trunk, means in said outgoing trunk for holding operated the line relay of said incoming trunk after disconnection of said operators equipment while said register sender is controlling the establishment of a connection with the called line in the automatic office, and means in said automatic ofiice for holding said line relay upon disconnection of said register sender from said outgoing trunk.

3. In a telephone system, subscribers lines, an

operators position comprising a telephone set and a numerical key-set, an incoming trunk and an outgoing trunk terminating at said position, means comprising a line relay operative upon seizure of the outgoing end of said incoming trunk for connecting the talking conductors of said incoming trunk to said operators telephone set, manually controlled means for interconnecting said trunks, manually controlled means for opera tively associating said key-set with said outgoing trunk, means comprising a selector switch connected to the distant end of said outgoingtrunk for establishing connection with a called subscribers line, a register sender for registering the number of a called line and for controlling the operation of said selector switch, means responsive to the interconnection of said trunks for connecting said register sender to said outgoing trunk, a source of current in said outgoing trunk, means responsive to the keying of a subscribers number and registration of the keyed digits in said register sender for disconnecting said incoming trunk from said operators position and for connecting the talking conductors of said incoming trunk to said source of current to hold said line relay operated, means efiective upon establishment of connection with the called line for disconnecting said register sender and for completing the talking connection over said incoming and outgoing trunks, and means in said selector for holding said line relay operated.

4. In a telephone system, subscribers lines, an operators position comprising a telephone set and a numerical key-set, an incoming trunk and an outgoing trunk terminating at said position, means comprising a line relay individual to the incoming trunk for connecting said incoming trunk to said operators telephone set, means for interconnecting said trunks, means comprising said key-set, a register sender and a selector connected to the distant end of said outgoing trunk for establishing connection with a called subscribers line, means for operatively associating said key-set with said outgoing trunk, means for thereupon operatively associating said register sender with said outgoing trunk for registration of the digits of the called line number as indicated by operation of said numerical keys, and means effective upon completion of registration of the called number for disconnecting said position equipment and for holding said line relay operated while said register sender is controlling the completion of connection with the called line.

5. In a telephone system, subscribers lines, an operators position comprising a telephone set and a numerical key-set, an incoming trunk and an outgoing trunk terminating at said position, means comprising a line-relay individual to the incoming trunk for connecting said incoming trunk to said operators telephone set, means at said position for interconnecting said trunks, means including said interconnecting means for operatively associating said key-set with said outgoing trunk, means comprising said key-set, a register sender and a selector connected to the distant end of said outgoing trunk for establishing connection with a called subscribers line, means for operatively associating said register sender with said outgoing trunk for registration of the digits of the number of the called line asindicated by operation of said numerical key-set, and means effective upon completion of registration of the called number for disconnecting said position equipment and for holding said line relay operated While said register sender is controlling the completion of the connection with the called line.

6. In a telephone system according to claim 5, means including said line relay for opening the talking connection over said incoming trunk.

JOHN ERNEST NORTON.

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