US1708934A - Electric signaling - Google Patents

Description

April 16, 1929.

E. T. BURTON ELECTRIC SIGNALING Filed Nov. 6, 1926 2 Sheets-Sheet l April 1'6, 1929. E. T. BUR'roN ELECTRIC SIGNALING Filed Nov. 6, 1926 2 Sheecs--SheeI 2 #Wen/aft' A fm .Patented Apr.' 16, 1929.

' UNITED STATES 'PATENT o Prior-:.4

EvEnETT T. BURTON, or JAcxsoN HEIGHTS, NEW roms, AssioNon To :BELL TELE'. rHoNE LABORATORIES, INCORPORATED, OE NEW yoiix, N. Y., A CORPORATION F NEW YORK.

ELECTRIC SIGNALING.

The invention relates toelectric signaling and particularly to carrier current telegra h iAnyobject of the invention is to simplify the operation and 'maintenance of carrier current telegraph systems. i

Another object of the invention is to reduce distortion in telegraph signals at terminal and repeater points.

The invention provides, a simple and 'etlicient telegraph system in which a single carrier frequency is employed for alternate transmission in two directions over each coinniunication channel. In transmitting sigi5 nals, the carrier current is impressed upon the line during a spacing interval and is cut of during a marking interval.A A vacuum,

tube receiving circuit or an alternating current receiving relay in each channel responds directly to the incoming and outgoing carrier currents.

Heretofore, in transmitting telegraph .signals it has been customary to control the receiving relay at the transmitting terminal a5 from the local direct currentfcircuit rather than from the carrier transmission circuit, and in receiving signals to rectify the in coming carrier currents to operate the receiving relay. By operating the receiving relay directly in response to incoming and outgoing carrier currents the' invention effects a material saving in signaling apparatus. Furthermore, operation of the near 'end sounder from the outgoing carrier allows dll ing signals lag on the make by the time of travel of the direct current relays and lag on the break by the time of travel ofthe alternating current relays.` According to the invention, the time lag` between make and the sending .operator to monitor directly on break signals is made uniform, thus eliminating distortion in the signals such as is commonly caused by the time ofarmature travel in the operation of repeater relays.-

The invention will be described` in connection with the accompanying drawings in which` similar reference characters designate similar parts in the several figures, and 1n which:

Fig. 1 is a diagrammatic illustration of a carrier current telegraph system including terminal and repeater circuits embodyinr the invention; .is

Fig. 2 is a diagrammatic illustration of a termlnal circuit which may be used in place of the terminal circuit shown in Fig. 1; and U Fig. 3 is a diagrammatic illustration showing modified terminal and Reference will rst be made to the multipleX carrier current telegraph' system shown in Fig. 1 which includes the west terminal a mid-line repeater inter connected by the transmission line section L1.

The usual east terminal, which is identical to the west terminal shown in Fig. 1, is omitted for the ysake of\ simplifying the showing, but in Apractice may be connected to the repeater by means of line section L2. u The terminal and repeaterl circuits may include a plurality of two-way communication channels ince these channels are identical except as to the frequencies which they employ, only detail and additional channels are merely indicated by the leads connected in parallel `with the line section L1 at the terminal and repeater.

Carrier currents of different frequencies are transmitted over the several channels of thesystem. Each channel requires but one carrier frequency for complete two-way communication, and hence fewer selective circuits are needed to separate the different channel frequencies than are needed in systems employing dii'erent frequencies in each direction.

The carrier telegraph channel which is illustratedin detail at the west terminal includes a band filter BF,L which passes currents of the frequency assigned to this channel and. suppresses currents of other freone channel is shown inrepeater circuits.

' cuited at the closed contacts of an auxiliary v yEF1, to the lower line conductor.

quencies. Similar band filters BF,- and BFI are associated with this channel at the repeater. The filters employed throughout the system may be of the ty e disclosed 1n U. S. Patent No. 1,227,113 to A. Campbell, issued May 22, 1917.

The apparatus at the west terminal 1n-v cludes a carrier frequency generator 5 which is connected to the band filter BF1 through the winding of an alternating current relay 6 which matchesthe impedance of the band filter. When no signals are being' transmitted, the carrier oscillator is short-cirswitch 7. through a resistance network 8.

vWhen no signals are being transmitted or received the relay 6 is deenergized, or in the markingosition shown in the drawing. In this condition the sounder 9' is energized over a circuit extending from grounded bat- :tery 10, through the winding of sounder 9,

contact and armature of relay 6 to ground. Incoming carrier currents pass through the upper conductor of line section L1, filter EF1, winding of relay 6,` switch 7 filter The current in this circuit causes the relay 6 to attract its armature, opening the circuit of sounder '9. When the switch 7. is opened and key 7 open, the outgoing currents from the generator 5 flow through relay 6 to line section L1, also causing the operation of the sounder 9. The sounder is thus operated in accordance with incoming and outgoing spacing and marking signals.

In case either terminal key is open, that is, when the oscillators at the respective terminals are not short circuited, carrier current flows through relay 6. If, therefore, the receiving operator at the east terminal wishes to break in-on the transmission from the west terminal, he opens his key and the transmittin sounder 9 fails to follow the operation o transmitting key 7 because relay 6 will be continually actuated.

The repeater includes an alternating current relay 11 associated with line section L1 and a similar relay 11 associated with line section L2. When no carrier currents are incoming at the repeater from either 'line section the circuits are as shown in the drawing. In this condition a relay 12, controlled by the relay 11, is energized over a circuit extending from grounded-battery 13, through winding of relay 12 to ground, and a similar relay 12 assoclated with the relay 11 is energized over a similar circuit. local carrier generator-14 is connected in circuit with resistance network 15 when no signals are received at the repeater, and is arranged to' be connected tol either line section whenever carrier current is received from the opposite line section.

the upper line conductor, filter BF lefthand winding of relay 11, armature and front contact of relay 12', filter BF, to the lower line conductor. The relay 11 thereupon operates, and upon opening its contact releases the armature of relay 12 by breaking the vlocal battery circuit previously traced. The relay 12 1n deenergizing closes its back contact, connecting the local oscillator 14'to the line section L2, so that carrier current flows over a circuit extending from the upper conductor of line section Ll through filter BF ri ht hand winding of relay 11', armature of ack contact of relay 12, left hand winding of relay 11', resistance network 15, oscillator 14, filter BF to the lower line conductor. In this condition the windings of relay 11 are connected in series opposin relation and hence this relay is not operate by the carrier current from the oscillator 14. When the carrier current on line L1 is cut-off at the end of a spacing signal, the relay 11 is deener ized and its armature returned to the mar ing position shown in the drawing, thus com leting the energizing circuit of relay 12 which disconnects the oscillator 14 from line section L2. It will be seen that the repeated spacing signals lag on the make by the time of travel of the armature of relay 12 since the carrier source 14 is not connected to line section L2 until the armature of relay 12 reaches its back contact. It will also be seen that the spacing signals lag on the break by the time of travel of the armature of relay 11, since the source 14 is disconnected from line section L2 when the armature of this relay reaches its contact. These relays are so constructed that the times of travel of -their armatures are identical and hence there is no bias in4 the repeated signals. The repeater is symmetrical in respect to the line sections L1 and L2, signals transmitted from east to west being repeated in the same manner as the signals transmitted from west to east.

Fig. 2 shows a modified terminal circuit arranged for connection to a subscribers loop. This circuit includes an alternating current receiving` relay 16 having two windings, and arranged to respond equally to the transmitted and received carrier currents. Only the right hand winding of this relay is connected to the line section L1 when signals are being received, and both windings are connected in series opposing' relation with the line section when spacing signals are being transmitted. The left hand winding of relay 16 is tapped at an intermediate point so that the differential ma etizing force produced by the transmitte carrier current in both windings is approximately equal to that produced by the weaker received current in the right hand winding. Hence this circuit arrangement eliminates inequality in the operation of the rela which would otherwise result from the di ference in value of the transmitted and received currents.

A direct current relay 17, also having two windings, is arranged to connect the carrier generator 5 to the line section L1, during a spacin interval and to disconnectt-he oscillator rom the line section during a marking interval. Then the circuit is in the condition shown in the drawing the left hand winding of rela-y 17 is connected to the subscribers loop over a circuit extending from the negative side of grounded battery 18, through a battery series resistance 18', closed contacts ot switch 7a, winding of sounder 9, high resistance 19, left hand winding or .re-v lay 17, battery resistance 20to 'the posltive side oit grounded battery 20.` The current Howing in this circuit is sufficient to operate the relay 17 but is insuilicientto operate the sounder 9. Y However, under such condition the right hand winding of relay 17 l1s connected to the subscriber s loo over alow re-v sistance circuit extending rom tlfrefnegai-` tive side et grounded battery 18, throughv resistance 18, closed contactsof switchv winding ot sounder 9, contact'and armature ot relay 16, right and lett hand windings oi l relay 17resistance-20 to the positive vside otgrounded battery 20. Thiscircuit carries an increased current suilicient to operate' the sounder 9. rlhe windings of relay 17 are wound in opposition and are so related in the number of turns that the eil'ect of the additional current fiowing through the subscribers loop during a marking interval,-wlliczh` is the condition shown in the drawing, is

substantiall neutralized in therelay 17 ,thus protecting t e core of this relayfrom exces-r sive magnetizing forces. '1 j e lncoming carrier currents which are passed by the band filter BF, pass through the right hand winding of alternating cur-v rent relay 16, causing this Lrelay tojiattract its armature and open the low resistancerem` ergizing circuit of the sounder 9. The currv rent which still flows from groundedbattery l,18, through resistance 18 switch 7a, sounder 9 resistance 19, left han winding of relay;

ergized but, as previously noted, is insuiiicient to operate the sounder 9. The sounder interval when carrier currents are received 9 is therefore deenergized during the spacing from the line section L1. `At the termination v of a spacing signal the relay 16 is deenergized, closing its contact and again establish-'- around the resistance 19.

ing the energizing circuit Afor thesounder9 In Order to transmit Signals, the transmit;

i ting key 7 is closed and the switch 7a opened.

sounder 9 and relay 17. The relay 17 in releasing its armature connects the generator 5 to the line section L1, permitting carrier current to flow over a circuit extendmg from the lower line conductor, through filter BF1 generator 5, resistance network 8, left hand winding of relay 16, back contact and armature of relay 17, right hand winding of relay 16, filter BF1, to the upper line conductor. rlhe current liow'ing in this circuit causes` the relay 16 to attract its armature. Wheri the transmitting key 7 ispagain closed, the relay 17 is energized over a circuit similar tothat previously traced .through the left hand windiner ot this relay and resistance 19, but inclut ing the contacts of key 7 instead-ofl switch 7,L which is now open. The current in this circuit, however, is insufcient to attract the armature of the sounder 9. The relayl 17 'in attracting its armature opens its back Contact, thus disconnecting the generator 5 from the line section L and deenergizes the relay 16, to complete the low resistance energizing circuit of the'sounder 9. The front contact of relay 17 is also closed, conditioning the circuit to transmit or receive further s1 nais. When no signals are to be transmitte switch 7a is closed.

This circuit also allows the receiving op erator to break in on the transmission by opening his local circuit and sending carrier over the line. If the east terminal operator breaks in, the sounder 9 will not follow the operation' of the west terminal key 7 since relay 16 remains actuated, preventing suiiicient current from reaching the sounder to operate it. vRelay 16 remains actuated because'current will be supplied to it either from the receiving station through the right hand winding of the relay or from the geni erator 5 through both windings of the relay.

In the modification of the invention shown in Fig. 3 space discharge tube detectors are employe in place of the alternatlngcurrent relays at terminal and repeater points. The operation of the system in receiving signals at the west terminal will first be described. Incoming carrier currents lpassed bythe band filter BF1, pass through the upper line conductor of line section L1, 17, andresistance 20 to groundedvbattery- 20, is suilicient to maintainv the relay*` 17 en-i* v,cuit induces a voltage in the right hand winding of transformer 21 connected in the inputl circuit of a three-element space,` discharge tubedetector 22. Space current is thus caused to How in the output circuit of this tube from grounded battery 25, through the right hand winding of relay 24, priing the sounder to release its armature. As

ary winding o f transformer 23 is connected lto an auxiliary windin` of relay 24, and a change of current in t is circuit causes a building up of flux which accelerates the opera-tion of the relay, as is common practice in telegraphy.. he relay 24 attracts its armature, opening the low. resistance energizing circuit ofthe sounder 9 and caus- *in the circuit of Fig. 2, the current flowing from grounded batter 20, through the right hand winding of re ay 17, resistance 19, 'winding of sounder 9, closedcontacts of switch the sounder. When the incoming carrier currents are cut off s ace current ceases to flow in the output circuit of the detector tube 22 and the relay 24 is deenergized, re-

establishing the energizing circuit of they sounder 9. l

In transmitting signalsfrom the west terv minal, the key 7 is closed and the switch 7. is o ened. y The key 7 is then opened, thereby eenergizing the sounder 9 and relay17. The .front contact of relay 17 is therefore opened and the back contact is closed, connecting the carrier generator 5 to the line section L1. Thev outgoing carrier current flows over a circuit extending from the lower line conductor, through filter BFI, generator 5, resistance network 8, left hand winding of transformer 21, back contact yand `armature of relay 17, central winding of transformer 21, filter BFI, tothe upper line conductor. The central and left hand windings of transformer 21 are connected in opposition and the back contact of rela 17 1s connected to an intermediate tap o the left hand winding of the transformer so that the magnetizing forcesl produced by the L transmitted and received currents in this transformer are approximately equal. The outgoing current produces an induced voltage in the right hand winding of transformerl 21 which causes space current to flow through the relay 24 in the output circuit of the detector tube 22, causing the relay 24 to attract its armature and open the energizing circuit of the sounder 9, which is also broken at the open contact of transmitting key 7. When the key-7 is again closed -the relay 17 is energized over a circuit similar to that .previously traced through the right hand winding of this relay and the winding of sounder 9, but including the contacts of key 7 instead of switch 7 a which is now open, current flowing in this circuit, however, is insufficient to operate the sounder. The relay 17 thereupon attracts its armature, disconnecting the generator 5 from the line section L1. Since space current ceases to flow in the output circuity of the detector tube 22, the relay 24 is deenergized, completing the low resistance energizing circuit of the sounder 9throu h both windings of relay 17. Also,

7, toground, is insufiicient to operate\\upper winding of this transformer which causes space current to flow in the output circuit of detector tube'28 which includes the winding of relay 27. The relay 27 thereupon attracts its armature, opening its back contact and closing its front contact, thereby impressing carrier current from the generator 14 upon line section L2 over a circuit extending from the upper line conductor, through filter BFS, central winding of transformer 26", armature and front contact of relay 27', lower winding of transformer 26', resistance network 15, generator 14, filter BF3 to the lower line conductor. In this condition the central and lower windings of transformer 26 are connected in series opposing relation and hence there is no increase in potential across the input circuit of the detector tube 28 and no current Aflows through ,the relay 27 in the output circuit of this tube. When the carrier currentl on line L,l is cut off at the end of a spacing signal the relay -27 is decnergized and its armature returned to the marking position shown in the drawing, disconnecting the generator 14 from the line section In order to prevent capacity coupling of the carrier current to the transmission line sections, the windings of relay 16 of Fig. 2 and the windings of balance transformers 21, 26, and 26 of Fig. 3 may be separated by suitable shielding devices.

Although the invention has been described in connection with certain specific embodiments, it is also susceptible of numerous other modifications without departing from the scope and spirit of the invention as defined by the appended claims.

What is claimed is:

1. A carrier current telegraph system comprising a transmission line over which signals are transmitted in both directions, a terminal including a receiving relay and a source of carrier current connected in series with said line, and means for rendering said relay responsive only to incoming signals, said means including means for short circuiting said source.

2. A carrier current telegraph system comprising a transmission line over which signals are transmitted in .both directions, a

lll.)

terminal including a receiving relay and a source of carrier current connected in series with said line, and a 'transmitting key adapted to directly short circuit said source when no signals are transmitted froml said terminal and to remove said short circuit to Arender said relay responsive to incoming signals.

v3. A carrier current telegraph system comprising a transmission line, a terminal including an alternating current relay in series with said line and responsive te incoming signals, a transmitter including a source oit sustained carrier current at said terminal, and means for connecting said source in series with said line and relay to actuate said relay in response to outgoing signals.

4.* A carrier current telegraph system comprising a transmission line having two conductors, a terminal including an alternating current relay in series with said conductors and responsive to incoming signals, a transmitter including a source of carrier current at said terminal, and means including a transmitting key for directly connecting said source in series with said conductors to actuate said relay in response to outgoing signals.. v

5. A carrier current telegraph system 'comprising a transmission line over which carrier currents are transmitted in both directions, an alternating current relay having a winding in series with said line and responsive to current transmitted in one direction, a source of carrier current for transmission in the opposite direction, means for .connecting said source to said line through said relay winding, and means for making the total magnetizing force of said relay produced by the current transmitted in one direction equal to the magnetizing force of said relay produced by the currents transniitted in the opposite direction.

G. A carrier' current telegraph system comprising a transmission line over which carrier currents are transmitted in both directions, and an alternating current relay having a winding in series with said line and responsive to current transmitted in one direction and a second 'winding adapted to be connected in opposition to said first mentioned winding in response to current transmitted in the opposite direction, said wind-- ings being proportioned to maintain the magnetizing force produced by the current in both windings approximately equal to that produced by the current in said first mentioned Winding.

7. A carrier current ltelegraph system comprising a transmission line over which carrier currents are transmitted in both directions,a circuit associated with said line and including a receiver responsive to incomand outgoing currents, and a plurality of electrical windings in said circuit prol ings.

portioned to maintain the operating forces exerted upon i said receiver by current in both directions approximately equal.

8. carrier current telegraph system comprising a transmission line over which carrier currents are transmitted in both directions, a terminal including an alternating current relay having a winding in series with said line causing said relay to be responsive-to incoming currents, and a second winding adapted to be connected in oppo sition. to said first mentioned winding both of said windings causing said relay to be responsive to outgoing currents, said windings being proportioned to maintain the magnetizing forces produced by the incornn .A ing and outgoing currents therein approximately equal.

9. carrier current 'telegraph system comprising a transmission line over which carriercurrents are transmitted in both directions, a terminal circuit including a source of carrier current, a relay adapted when deenergized to connect said source to said line, a receiver connected in series with said relay, and means responsive to incoming carrier currents to actuate said receiver without deenergizing said relay.

10. A vcariier current telegraph system comprising a transmission line over which signals are transmitted in both directions, a terminal circuit including a carrier current generator, a relay having two windings adapted when deenergized to connect said enerator to said line, an energizing circuit or one winding of said relay includinga receiver and a source of current suilicient to operate said relay but insuificient to operate said receiver, an energizing circuit for said receiver including 'said source and both,

windings of said relay, and means responsive to incoming signals to open and close said second mentioned energizing circuit.

l1. A carrier current telegraph vsystem comprising a transmission line over which signals are transmitted in both directions, a terminal -circuit including a carrier current generator, a relay having two windings adapted when deenergized to connect said generator to said line, an energizing circuit including a receiver in series with one winding of said relay and a source of current sufficient to operate said relay but insuiiicient to operate said receiver, and an energizing circuit for said receiver including said source and both"windings of said relay, the windings ofsaid relay being proportioned to maintain the magnetizing force produced by the current in said iirst mentioned winding approximately equal to the magnetizing force produced by the current 1n both wind- 12. comprising two line sections over which carrier currents are transmitted in both di- A carrier current telegraph system.

rections, a device having an armature re. sponsive to carrier currents transmitted' over one line section, a relay adapted to deenergized upon the energization of said device, a source of carrier current, means to connect said source to the second line sec" tion upon the deenergization of said. relay7 and to disconnect said source from said sel ond line section upon the deenergizatlonof said relay, and means including said first means and said armature of saidD device for making the intervalbetween signals over said second line section of the same duration as the interval between signals over said y tions, an alternating current rela v irst line section. s f

13. A carrier current telegraph s stem comprising two line sections over whic carrier currents are transmitted in both direcresponsive to carrier currents transmitte over one line section, a direct current relay adapted to be deenergized upon the energization of tions, an alternating current relay having an armature operative in response to carrier currents transmitted over one line section, a direct current relay adapted to be deenergized to release its armature upon the energization of said alternating current relay, and a source of carrier current adapted to be connected to the second line section upon the deenergization of said direct current relay and adapted to be disconnected from said second line section upon the deener ization of said alternating current relay, sai relays bein so proportioned that the times of travel o their armatures are substantially equal.

15. A carrier current, telegraph system comprising a transmission line over which signals are transmitted in both directions, termmal circuits each including a carrier current generator, a recorder of signals received and transmitted over said line, an alternatin current relayoperating said recorder, said incoming and outgoing signals actuating said alternating current relay, and means at each terminal lfor disabling the operation of said alternating current relay and said recorder at the opposite terminal when signals are being transmitted from the opposite terminal.

In witnessAwhereof, I hereunto subscribe my name this 29th day of October A. D.,

EVERETT T. BURTON.

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