US2332966A

US2332966A - Code call system

Info

Publication number: US2332966A
Application number: US432273A
Authority: US
Inventors: Edson L Erwin
Original assignee: Bell Telephone Laboratories Inc
Current assignee: AT&T Corp
Priority date: 1942-02-25
Filing date: 1942-02-25
Publication date: 1943-10-26
Anticipated expiration: 1960-10-26

Description

m3231943. LE, L ERwm x 2,332,966

CODE CALL SYSTEM Filed Feb. 25, 1942 `5 sheetsjsheet 1 d L LL L L L u LLL jd FIG /N VE N 70k E. L. ERw/N ATTORNEY Oct. 26, 1943.

E. L. ERWIN GODE CALL SYSTEM 1 Filed Feb. 25,v 1942 5 Sheets-Sheet 2 ATTORNEY Oct. 26, 1943. l

v E. L. ERWINl CODE CALL SYSTEM Filed Feb. 25, 1942 5 Sheets-Sheet 5 /NVENTOR E. L. ERW/N A7' TORNEV Ocfn 26, 1943. E. L. ERWIN '2,332,966

CODE CALL SYSTEM Filed Feb. 25, 1942 l 5 Sheets-Sheet 4 JMW? Oct. 26,- 1943. E. L. ERwlN 2,332,966

` A QODE CALL SYSTEM Filed Feb. 25, 1942 5 sheets-sheet 5 FIG. 5

/NVEN7UR ELE'RW/N .13Vy

ArTo/PNK code signal devices.

Patented Oct. 26, 1943 UNITED STATES PATENT OFFICE 2,332,966 conn CALL SYSTEM Edson L. Erwin, Towaco, N. J., assigner to Bell Telephone Laboratories, Incorporated, New York, N. Y., a corporation of New York application February 25, 1942, serial No. 432,273

Claims.

This invention relates 4to automatic private branch exchange systems and more particularly to `code signaling arrangements for such ex-` changes of the character described, for example, in the Reissue Patent 17,006, M. L. Nelson, dated June 9, 1928, which system provides facilities whereby certain persons may be called when they are absent from their office and in some other department or location inthe factory, store` or other establishment served by theprivate branch exchange.

An object of the present invention is to improve i systems of the above character whereby greater flexibility of operation is obtained and additional service features are provided.

` One feature of the inventionresides in means for limiting the number of times a transmitted code is repeated to operate the bells, or other A related feature resides in means, operated at thetermination of a predetermined number of code signal repetitions, initiated by a subscriber, to signal" the exchange attendant if the called party has not kanswered in the meantime.

Another feature residesin` means for enabling the attendant to connect to and directly control the code signaling equipment from her position independent of the automatic switching equipment, and also to connect thereto central oflice or tie trunks, incoming to and terminating at her position whereby the code signaling equipment may be controlled over said trunks independent of both the automatic switching equipment and the attendant.

Another feature resides in means whereby when' the called party, in responding to his code, obtains a connection to the calling party through the code signaiing equipment, a battery reversal toward the calling party is effected which reversal is required in some cases when certain types of trunks are connected to and control the code l `the code dialed will be the same regardless of the number of impulses forming the first and last digits of the code, for example the interval between successive repetitions ofthe code 1--1--1 will be substantially the same as the interval between successive repetitions of the code 5-5-5. k

Other features of the invention will appear from the following description and appended claims. i

An understanding of the invention will be obtained from the following description when read in connection with the accompanying drawings, the iigures of which, when arranged in accordance with Fig.. 6, show a complete system in accordance therewith, Fig. l showing in schematic form an automatic private branch exchange with two subscribers lines and an incoming ytrunk from a central omce, or another private branch exchange, having access to the automatic equipment; Fig. 3 shows a manual switchboard position associated with the private branchexchange, and Figs. 2, 4 and 5 vshow the arrangement of the code signaling equipment, containing the novel features of the invention, which is arranged to receive andV translate three-digit dial pulses into s code signals of the same number of digits.

A description ofthe system and its operation follows: Referring to the drawings it will be rst assumed that the subscriber A, Fig. 1, has called a certain other subscriber X, not shown, by dialing his station in the usual manner and, having received no response, has released the connection and decided to attempt to reach the wanted party by sending out his preassigned code to operate a plurality of bells or other signal devices Sl, S2, etc., located throughout the factory, store or other establishment served by the private branch exchange. It will be further assumed that the preassignecl code of subscriber X is 323.

When the receiver is removed from the hook at station A, the line iinder (not shown) will hunt for and seize the calling line after which it will `be extended to a trunk terminating in an idle and all succeeding terminals of the iirst leve1 are made permanently busy.

When the brushes 4, 5 `and 6 of switch Cl `are raised` to the first level and rotate to the first terminal under control of the subscribers dial, if the code switching apparatus is idle, the circuit of the rotary magnet will be opened in the usual manner and the switch will stop thereon. If the code switching equipment is busy the rotary magnet will continue to step the brushes around past all the succeeding permanently busy contacts into the busy position to give the subscriber a busy signal all of which is well-known practice and needs no further explanation. lf the switch stops on the first set of contacts due to battery on the sleeve conductor 3 which can be traced from relay l, conductor 8, con'tacts 9 of relay iii, conductor il, contacts I2 ci relay I3, and conductor I4 to the sleeve conductor 3, relay 'I will operate due to ground from the preceding switch applied through brush E of connector Ci. Closure of contacts I53 of relay 'i connects battery to light the busy lamp E64 at the attendants switchboard position in a circuit which can be traced from battery, conductor |65, contacts H53 of relay 1, and conductor |66 to ground, through the busy lamp H54 thus indicating to the attendant that the code call circuit is busy. rthe calling subscribers line will also be cut through to relay I5 which operates in series therewith over contacts I5 and Il of relay I 8. Operation of relay I5 operates relay I9 in an ob vious circuit which latter relay at its contacts operates slow-to-release relay 20. VRelay it! closes its contacts 22 thereby completing a circuit to operate relay from ground, contacts 23 of relay I9, contacts 24 of relay I8, contacts 22 of relay 2D, and winding of relay 25 to battery. Relay 25 in operating closes its contacts 25 to connect battery in series with resistance 2l to the sleeve conductor 28 which is connected in multiple to the first terminal in the second level of switches CI, C2 and C3 for a purpose to be hereinafter referred to. Relay 25 in operating closes at its contacts 29 an obvious circuit to operate relay 30 (Fig. 4). Relay 25 also closes its contacts 3l to connect the back or pulsing contacts 32 of relay I5 to the Winding of relay 33 (Fig. 5), the circuit for which includes contacts 34 of relay I9 and conductor 35.

Relay 30 in operating operates relay 36, the circuit for which can be traced from ground, contacts 3l of relay 39, conductor 38, contacts 39 of the oil-normal switch ONI associated with selector SI and contacts 49 of relay 4I to battery through the winding of relay 35. Relay 3B in operating closes its contacts thereby completing a circuit to operate relay 42 which can be traced from ground, contacts 31 of relay 3b, conductor 38, front contact of relay 35, contacts 43 and winding of relay 42 to battery. Relay 42 in operating closesits contacts lll to lock itself operated to ground on `conductor 3B supplied at contacts 3l of relay Sli, and at its contacts 45 connects the rotary magnet 46 to conductor 35 which eX- tends to the pulsing contacts 32 of relay I5. l

When the subscriber releases the dial for the rst digit (3) of the assumed code, relay I5 follows the pulsesand alternately operates relay S3 and the rotary magnet 46 which` magnet steps the brush of selector SI ahead to the third. contact. When the selector SI moves volf-normal, it opens contacts 39 of the off-normal switch OFI which interrupts the original operating circuit Vof relay 36but this relay (36) is slow to release and holds operated due to the intermittent operation of relay in step with magnet 46. When the rst digit is finished relays 33 and 36 release. Relay 3d opens lits contacts thereby removing a short circuit from the winding of relay 4I which was connected when relays 36 and d2 operated. This short circuit can be traced from the right-hand terminal of the winding of relay el, contacts Ill and l5 of relay 42, front contacts or relay 5B and contacts 48 of relay il to the lefthand terminal of its winding.

When relay SS releases this sh'ort circuit is removed and relay il now operates in a circuit troni battery, winding of relay lli, contacts 41 and it of relay 422 and conductors 38 to ground at contacts 3? of relay Sli. When relay il opcrates, relay 35 reoperates in a circuit from ground on conductor 58, contacts of relay 5I, contacts 52 of relay il and winding of relay 35 to battery. Reoperation of relay 5E new operates relay 53 in a circuit which can be traced from ground on conductor 33, front contacts of relay 3d, contacts 54B of relay 4I, contacts 55 and winding of relay 53 to battery. Relay 53 in operating locks at its contacts 55 to ground on conductor Sii and closes its contacts 57 to connect the rotary magnet t@ for selector Sil to the pulsing lead 35. Operation ci relays and 53 completes a short circuit around the Winding of relay 5I which can be traced from the lower terminal of its winding and its contacts 53, contacts 5G o relay (il, front contacts of relay 36 and contacts 55 and 53 of relay 53 to the upper terminal of the winding of relay 5I.

Dialing of the second digit of the code (2) causes relay 33 and magnet 5i! to follow the pulses. Magnet Si! steps the brush of selector S2 ahead to the second terminal. When the selector S2 moves off-normal it opens the contacts (i9 of the olf-normal switch ONZ which interrupts the operating circuit of relay 36 but this relay, as before, holds operated due to the operation of relay 53 in step with the pulses. When the second digit is finished relays 33 and 3B again release and the release of relay 3B opens the previously traced short circuit for relay 5i which now operates in the following cir- 'cuit:.battery, winding of relay 5l, contacts 59 and 5t of relay 53, to ground on conductor 33.

In a like manner, as previously described, operation of relay 5I causes relay V3% to again operate which causes relay 6I to operate, lock, and connect the rotary magnet of selector S3 to the pulsing lead 35. Relay 54 is also short-circuited.

Dialing of the third and last digit (3) of the code steps the switch S3 ahead to the third terminal and at the end of the pulsing, relays 33 and Y 36 again release thereby removing the short circuit from relay t@ which thereupon operates to open its contacts t5 thereby preventing further dialing from moving switch S3.

When relay 6 operates at th'e end of the code impulses, it closes at its contacts EB, a circuit to initiate a self-interrupted stepping of switch D which circuit can be traced from ground, contacts t? of relay 3i) (Fig. 4), contacts 58 of relay 59, conductor lt, contacts 66 of relay '65, conductor ll, contacts l2 of relay '53, contacts i4 and 'l5 of relay l5, conductor 1l, contacts i3 of stepping magnet 'lil and winding of relay 853 to battery, Relay 83 operates and closes its contacts SI to complete a circuit to energize magnet lil which canbe traced from ground on conductor lll, contacts 8l of relay 89, conductor 82, contacts 5t of relay "E3, conductor 8G and winding or magnet 'i9 to battery. Energizaticn of magnet 'i9 steps the brushes of switch D ahead and opens its contacts 'i3 thereby causing relay @il to release and open its contacts @I whereupon magnet 'i9 is deenergized and releases and closes its contacts 'I3 which recloses the circuit 2,832,966 of relay 80I which operates and closes its con- `tacts 81 which in turnreenergize magnet 19 to move switch D ahead a second step.` This stepping continues to advance the brushes of switch lI J at a very rapid rate. Selector switches Sli, S2 and S3 serve as registers for the digits of' the code dialed which in thekpresent" case was 323, and therefore the ,brush of switch SI` is standing on the` thirdA terminal, the brush of S2 on the second terminal i in the `arc Dd'ofthe selector switch D. At this point it may be mentionedv that for practical reasons codes having individual digits greater than the digit I are not desirable and therefore the system disclosed is' so arranged and conse 'quently the switches Sil, S2 and S3 which' serve .to register the ydigit pulsesl have their first five terminals only connected to terminals of the arc D4 and thek remaining terminals of each of the `switches SMS2 and S3 are connected-in multiple to a conductor 85 for a purpose hereinafter described.

When `the brush corresponding toarc D4 engages terminal. 88, which is grounded by the setting of `switch Sl, a `circuit is completed to `operate Vrelay 16 (Figi 4) which includes conduc- 13012.89; Whenl relay 16 operates, it opens its contacts thereby interrupting the previously traced' circuit4 for stepping. magnet 19 whereupon theswitch D'stops. Relay 16 also closes its contacts 90 to operate relay 13', the circuit of which `can be traced from ground at contacts `31 of relay `30, conductor 9|, contacts 90 of relay 16 and .winding of relay I3 to battery. Relay 13 closes `its contacts 92` to lock relay 11S operated in a circuit including, conductor 93,: the third terminal and' bruslr of are' D3, and: contacts? 811 of relay 30 4toyground. l=telay`13y also closes its? contacts 94 Vto initiate sequential operation of interrupter relays 95;; 96 and 91 which function as follows: closure of contacts 94 of relay 13 completes a `circuitrtooperate relay SFr-whichcan be traced from` ground,`contacts 61 of. relay 30, contacts 68 of rela-y 69,? conductor 98, contacts 94' of relay 13 'and the back contacts of relay 915 to the Winding'of'relay 95. Relay 95' operates in. this circuit Aand closesan obvious circuit to operate relay 96 which performs several functions, i'. e., at its contacts 99; it closes ar circuitv to operate relay |00 which can be traced from ground, contactsI 99 of relay 96, contacts |0| ofY relay 161 and winding of relay |00 to battery. Relay |00 in operating 'closes acircuit to energize the signal bells SG1, 'SGZ and any others that may be connected in multiple therewith- Closure of contacts |02 completes a circuit to connect tone source 'l-Sv to the Magnet 19 moves-switch D ahead another step in connection with the fourth terminal.- Operation of relay 96' also closes its lowermost contacts |01 thereby operating relay 91 which opens' its upper backcontacts to release relay 95 which, in turn, opens the circuit of relay 96 which `also releases thereby opening its contacts 99, |02,` |05' and |01'to release relay |00 and open the cir-' cuit for the signals SGI, etc., to disconnecttone from the trunk CT, to release the stepping magnet of switchD, and to release relaySl. Relay 91 is slow to release butwhen it recloses its back contacts, the preceding cycle of operation is repeated whereupon the signals SGI, etc., are again operated,`to`ne is again transmitted to the calling subscriber and switch D moves ahead another step to the flfthterminal and relay 91 is operated to again release relay 95 which, in turn,

trunk CT as an indication tothe* calling subscriberthat' the code signals are operating. `The circuit for this tone connection can' be traced from the source TS, closed contacts ofrel'ay |03, which relay was operated when relay 4| closed its contacts |04 at the conclusion of the pulses representing'the rstdigit. The closure of contacts |505 of relayv 95 completes a circuit to reenergize stepping magnet 19, independently of relay 80, which can be traced from ground, contacts `|505A of relayv 99, contacts- |0|2 of relay 13, conductor 84",` and winding `of magnet 19' to battery.

releases Vrelay 9-1 to recondition the chain of

relays

95, 96 and 91 for a thirdcycle of operation which again functions as previously described,` including driving the switch D ahead to the sixth terminal. As will be noted, the sixth terminal of arc D3 is dry, i. e., is disconnected from conductor 93 which, in turn, is connected throughrelay 16 to battery and therefore wheny the brush steps off the fifth terminal and engages the sixth terminal, relay 1S releases which disables the signal `devices SGI, etc., and the tone circuit to the calling subscriber.

At this point'it should be mentioned that when the' switch D moves into its fth position, a holding circuit was established forrelay 13 Vindependent of relay 16 which can be traced from battery, winding and contacts`|08 of relay 13, conductor |09, the fifthr terminal and brush of arc lDI and conductor Siiv to ground' at contacts 81 of relay 39.' And, therefore, when relay 16 releases, as above mentioned, relay13 remains operated thereby holding the circuit prepared 4to again operate relay 95 when relay 91 releases and therefore another cycle of operation of relays 95, 9S and 91 takes place to energize magnet 19 and move the switch D ahead to the seventh position whereupon the brushof arc DI moves off `the sixth terminal which opens `the previously described locking circuitl for relay 13 which now releases.` This pause at the end of the digit while lswitch D movesV over terminal 6`without operating the signal bells SGI, etc., and without transmittingr a tone pulse to thecalling subscriber isfor the purpose ofintroducing the space betweenl the `first and second digits of the code sounded which will be referred toi later.

When relay 19 releases it recloses a circuit to cause stepping magnet 19 to operate under control of relay Si) and to advance the switch D until thev brush or arc Dll engages the tenth terminal rninal`- at which time relays 15 and 13 operate in succession and cause relays 95, 96 and 91 to function to again sound the signals SGI, etc., and transmita toneto the calling subscriber.

The brush of arc D3 advances from the tenth to the twelfth terminal as before described under control of relay 96 thereby sounding the signal devices twice after which relay 'I6 releases due tothe brush of arc D3 moving off the eleventh terminal thereby opening the circuit to the sign'aldevices and the tone circuit. The switch D, however', takes another step due.' tol the relay 13 being held' by the brush of arcDlwhile the switch moves` through itseleventh and twelfth positions thereby introducing a pause between thel second The rst three times relay Slt operates; the

signal devices SG are sounded, tone is connected to the calling subscriber land the magnet i9 is energized to drive the switch D ahead one step. When the brush of arc D3 moves off its seventeenth terminal, relay 'I6 releases but the brush of arc DI closed in its seventeenth position a holding circuit for relay 'I3 whichV held the circuit closed to continue the sequential operation of

relays

95, 95 and 91. Due to the fact that the remaining terminals of arc DI- are strapped to-v gether relay 'I3 will remain operated and relays 95,Y 95 and 9i will continue to function to drive the switch D around until it passes ofi its last terminal whereupon the relay F3 releases. This stepping of the switch D over terminals I8, i9, 2t,

2l and 22 of arcfDI provides a suitable pause between the third digitof the iirst code cycle and the iirst digit of the second code cycle.

When relayli releases the switch D, vwhich now stands in its iirst position, again continues to advance under control of relay 8B and magnet lil until the brush of arc De again reaches its iirst grounded terminal whereupon the circuit functions in the manner previously described to send out a second, third, fourth, and fifth cycle of code signals provided the called subscriber has not answered in themeantime.

Called :party answers kWhen-the called party hears his code signal e( and Wishes to answer, he goes to any convenient nearby telephone of the private branch exchange, station B for example, and dials a certain predetermined code to Vcause a connector C2 to seize terminals connected to the trunk CT over conating,.relay H2 closes, at is contacts H3, an obvious circuit to operate relay i8 which latter relay closes its contacts IIfl to operate relay il from ground at contacts il@ of relay IIZ. Relay vI3 also locks at its contacts H5 to ground at contacts II'l of relay 2B. By opening contacts IS and Il and closing its contacts IIB and IlS, the battery supplied through relay 32 to trunk CT is reversed in polarity which, in the present example, performs no essential function, but is effective in oase an incoming repeating tie trunk RTT, Fig. l, has seized the code trunk CT through connector C3 to cause the incoming trunk to cut through into the talking condition. Relay i8 in operating also closes its contacts to connect a condenser across the midpoint of the left-hand winding of the transformer IEE. Relay it also opens at its contacts 2l! the operating circuit for relay 25 which relay, however, is held locked to ground supplied by the brush of arc D2 until the code circuit finishes they code cycle being transmitted. When the switch D reaches its last position of the cycle, relay- 25 -releases thereby opening its contacts k29 to release relay 30 and prevent further operation ofswitch D and further signaling.l y

Relay IE5 in operating locks over its upper winding to ground at contacts 2l of relay I9 and releases relay 2t which opens its contacts |23 to remove the short circuit from the right-hand winding of repeating coil i222, opens the tone lead at its contacts IZfi, and opens at its Vcontacts II1 the locking circuit i'or relay i8 which releases. The sleeve conductor 3 of the calling party is grounded at contacts' H25 of relay IS and also at contacts I2@ of relay Ii 2 so that the trunk CT will not be reseized by another connector until both the calling and called stations have disconnected. The calling and called subscribers are now connected in a conversational circuit.

Called party jails to answer minal of the arc thereby completing a circuit to operate relay l2'l which can be traced from ground at contacts Si of relay Sii, conductor 8S, brush. of arc D5, conductor 23, contacts |29 and winding of relay l2'lt0 battery. Relay I2'I locks up to ground at contacts Sl of relay S@ and closes its lower contacts to connect relay ISB to conductor ISI which is connectedr to the twelfth terminal of arc D5 and therefore when the switch D makes a second revolution and the brush of arc D5 engages this terminal, relay 36 operates to lock in multiple with relay l2? and prepares a circuit for relay 32 which is closed when switch D makes a third revolution and the brush of arc D5 engages its eleventh terminal.' iIn a like manner relays IBS and i3d .operate in succession as the switch D makes successive revolutions and l the brush of arc D5 engages its terminals 6 and 5.' When relay itt operates, it closes'its lower contacts thereby connecting relay 69 to conductor I which terminates on the next to the last terminal 2l of the arc D5 and therefore when the switch D arrives in that position, ground is connected, as before, to this conductor and relay 69 operates thereby opening its contacts 68 to disable the stepping of switch-D and causing its brushes to remain in position 2l. Relay 69 also closes its contacts It thereby connecting ground to conductor H36 which extends over contacts I3'I of relaylii, conductor 33, contacts E33 of relay I (Fig. 3), contacts it@ of relay i3, to battery through lamp It! at the private branch exchange attendants position.

Upon noting lighted lamp lill the attendant plugs into the talk jack M2 with one of her cord circuits thereby operating relay I3 over the auxilary contacts M3 of the talk jack. Relay I3 opens at its contacts 240, the circuit for the lamp lill, grounds the sleeve o jack M2 by [closing contacts Idil and'by closing its contacts It operates relay i3 in a circuit including contacts M5 of relay l and conductor Ml.

Relay i8 in operating opens its contacts 24 to release relay 25 and closes its contacts H4 to operate relay ll whichl relay locks up t0 relay Non-existent code If the subscriber calls a number containing a digit higher than the limits for which the system is set, which in the present example is 5, all the terminals above 5 of switches Sl, S2 and S3 are connected together and to relay 69 whereby if a number containing the digit 6, for example, is dialed as soon as the particular switch SI, S2 or S3 passes out of its fifth position, relay 69 will operate to prevent the operation of the signals SG and to call in the attendant as previously described.

Code call originated by attendant The attendant may initiate a code call by plugging one of her cord circuits, LI for example, into the talk jack |42, and the calling end of another pair oi cords L?. equipped with a dial, into the dial jack |48.

When the cord LI is plugged into jack |42, relay |3 operates in the following circuit, battery, winding of relay I3 and contacts M3 oi the jack to ground at contacts Ille of relay 'I. Relay |3 grounds the sleeve of the jack and cord and closes at its contacts |55 a bridge including impedance coil |5| across the trunk to operate the line relay I5 in the code signaling equipment.

`When a plug o1" another cord circuit L2 is connected to jack |43, relay lll operates from the Sleeve of the plug over the `auxiliary contacts of the jack and contacts |52 of relay l. Relay Il] in operating disconnects, at its contacts |53 and |54, the tip and ring of the jack |42 from the trunk CT and closes its contacts |55 and |60 to operate relay |55 ii the dial key of the Cord circuit is operated in a circuit from ground, upper winding of relay l5, contacts I5 of relay I8, upper left winding of transformer |22 and the tip conductor of the trunk CT, contacts |55 of relay lil, lower winding of relay |55, tip spring of jack |48, through the closed contacts of the dial, back over the ring of the jack, contacts |60 of relay l0, ring conductor of the trunk, lower left winding of transformer |22, contacts |1 of relay I8, and lower winding of relay I5 to battery. Relay |55 `loclrs up over its upper winding and contacts |51 to ground at contacts |58 of relay l and by closing its contacts |59 short circuits its lower winding thereby removing the resistance oi this relay winding from the pulsing circuit which includes relay l5. Relay |56 in operating also opens at its lower contacts the bridge including impedance coil I| connected across the trunk when relay I5 operated. This, however, does not release relay I5 as that relay is now held operated under control of the dial supervisory lamp in the cord fcircuit LI., Re.- moval of both cords L and L2firom theirgre.- spective jacks permits thev circuit to reStQre, to normal.` v` i Emergency interception kbycttiendant Iii the attendant wishes to use the code call circuit in an emergency which is indicated `busy bythe lighted condition of the' busy lamp |64, she may plug into the jack |42 with a cord circuit and talk tothe parties in conversation requesting them-` to disconnect; The` attendant then withdraws the plug of her'cord circuit and waits for the busy lamp |64 to be extinguished which indicates that the code call circuit is now idle after which she may originate a code call in the manner previously described.

Time interval between digits of the code sounded and between successive repetitions of the code It wil1 be noted that the movement of switch D is very rapid while driven by the operation and release of relay and at a relatively much slower rate by the sequential operation of

relays

95, 96 and 91 and therefore the pause between digits oi the code and also between successive repetitions of the code is determined by the movement of the brush of arc D1 over the `bridged terminals 5, I2 and |8 to 22 and substantially independent of the time consumed in the rapid movement of switch D under self-interruption, i. e., by the operation and release of relay 80.

What is claimed is:

l. In a telephone system, automatic switches, a code selecting switch accessible to said automatic switches, signal devices, means for controlling said code switch from said automatic switches to repeatedly operate said signal devices in accordance with a predetermined code and to disable said code switch when said signals have repeated said code a predetermined number of times.

2. In a telephone system, automatic switches, an operators position, a code selecting switch accessible to said automatic switches and position, a signal device at said position, other signal devices, means for controlling saidcode switch from either said automatic switches or operators position to repeatedly operate said other signal devices in accordance with a predetermined code, and means for disabling said code switch when said code has been repeated a predetermined number of times and to actuate said position signal when an automatic switch has control of said code switch.

3. In a code calling system, automatic switches, a plurality of code register switches accessible to said automatic switches, pulse transmitting means for controlling said automatic switches and seize control of said register switches and to thereafter sequently set said register switches in accordance with a, predetermined code, a selector switch, signal devices controlled thereby, means responsive to the setting of the last register switch to cause said selector switch to cyclically operate said signal devices in accordance with the code pulses registered, and means for introducing a substantially uniform time delay between the digit operations of said devices regardless of the number of operations representing each digit and other means for introducing a different uniform delay between each `operation cycle regardless of the number oi operations representing the last digit of one cycle and the number ci operations representing itsfrstadigit of the succeeding cycle.

4. In a telephone system, automatic switches, an operators position, a code sending switch accessible to both said automatic switches and to said operators position, signal devices, means for controlling said code Switch from said automatic switches to repeatedly operate said signal devices in accordance with a predetermined code, and means for controlling said code switch from said operators position to operate said signals independent of said automatic switches.

5. In a telephone system, automatic switches, an operators position, a code sending switch accessibleto both said automatic switches and said operators position, rst signal devices, means for controlling said code switch from said automatic switches and repeatedly operate said rst signal devices in accordancewith a predetermined code, means foi1 controlling said code switch from said operators position to operate said signal devices vindependent of said automatic switches, a visual signal device located at said operators position, and means responsive to seizure of said code switch by said automatic switches to display said Visual signal.

' EDSON L. ERWIN.