USRE16615E - Automatic telephone system - Google Patents

Description

\ May 3.1927.

R 16,615 H. HOVLAND i AUTOMATI C TELEPHONE SYSTEM rigina-l Filed Dec. 29, 1924 Reissued May. 3, 1927.

UNITED STATES PATENT OFFICE.

HENRY HOVLA'ND, OF FLUSHING, NEW YORK, ASSIGNOR TO WESTERN ELEGTRIG COM PANY, INCORPORATED, OF NEW YORK, N. Y'-, A CORPORATION O]? NEW YORK.

'AUTOMATIC TELEBHONE SYSTEM.

Original No. 1,614,959,,dated January 18, 1927, Serial No. 758,592, filed December 29, 1924. Application for reissue filed March 23,

This invention relates to machine switching telephone exchange systems, and more particularl to systems employinggrounded signaling. irom the "substations, and is particularly adapted for systems wherein the substations are provided with coin collectors.

The object of this invention is to permit a callingparty to buildup arconnection to certain lines, for example, to the operator, without depositing a coin while preventing the calling subscriber from building up a connection to an ordinary line, unless the coin is first deposited.

A further object of this invention is to provide means to prevent the extension of a calling line to a desired called line if the calling subscriber attempts to simulate the deposit of a coin. V

In accordance with this invention all lines are reached via a certain group of selector switches, the ordinary lines via certain levels of said switches and the free lines via certain other levels of said switches. Each switch is provided with a test relay which is. responsive to the deposit of a coin at the calling substation on calls to an ordinary line. This relay in responding prepares the switch to extend the connection to the subsequent switch or switchesof the train. On calls to free lines an alternative circuit is provided for. causing said test relay to respond and permit the establishing of a connection with a tree line. If for any reason the test relay does not respond due to the absence of the required circuit condition, the selector switch operates in accordance with its secondarymovement and advances to a setting known as the 11th rotary step position, where it remains until the calling substation disconnects.

In the drawing comprising but a single sheet, the invention is diagrammatically set forth. The callingsubstation is represented at 1 and a typical called substation art- 2. The selector switch S1 is wired inaccordance with this invention and has access to another selector switch S'2,'which in turn has access to a connector C The invention will be more readily-understood from a detailed description. of the operation of the system.

Ordinary call.

\Vhen the receiver is removed at the sub- 1927. Serial No. 177,777..

opera'te it. Relay 24" operated. closes an obvious circuit to operate slow to release relay 25. A circuit is now closed to operate relay 19 by way of 54, and 49., Relay 19 operated locks by way of its arma1ture'8, condiictors 4 8. and 55 and' armature 49 of'relay '25 to ground. Relay 19 operated renders the interrupter 9 ineffective. The operation of relay 19 closes an obvious circuit to operate relary 18, which locks'unjder control of relay 11" and connects ground by way of the retardation coil 17 and conductor 53 to the line finder LF to prevent the line finder LF 'from releasing.

The dial at the calling-substation 1 is now operated and released in accordance with the first. digit of the number of the called line. As the dial returns to normal the loop at the calling substation 1 is interrupted, thus producing impulses in the circuit including the impulse relay 24, which relay follows the impulses. l/Vhen relay 24 releases,- a circuit is completed by way of-its armature and backcontact to operate the primarymagnet 27 and slow to release relay 26 in series. Relays 25 and 26 are made slowto release, so that they will remain operated during the impulse period. Each time the primary magnet 27 operates, a-brush rod (not shown) carrying the brushes 20, 21 and 22 is advanced step by step, in accordance with the primary movement of the selector switch S1, depending upon the number of impulses produced by the calling dial. During the first step of the selector rod, the offn-orma=l contact springs ON are closed, closing a circuit to operate the marginal relay 38. This circuit may be traced under control of the off-normal contact springs ON, alternate contacts of'relay 26 to ground at the left contact of relay 25. Relay 38 0 crated locks under control of thesecon ary magnet 36 and its own right hand armature and front contact to ground under control of relay 14. When the dial of the calling substation 1 returns to normal, relay 24 remains operated and relay 26 releases. Relay 26 released closes a circuit to operate the secondary magnet 36 and relay 3'7 in series under control of the normal contacts of relay 26 and armature 49 of relay 25. The operation of the secondary magnet 36 advances the brushes 20, 21 and 22 of the selector switch S1, one step in accordance with the secondary movement of the switch. The operation of relay 3? substitutes the right winding of relay 23 and the winding of relay 72 for the right winding of relay 24 in series with one side of the call ingline loop. If a coin has been deposited in the coin controlled mechanism at the calling substation 1, a circuit will be established from battery, through the winding of relay 23, winding of marginal relay 72, through a pair of contact springs 57 and 58 closed by the deposit of the coin at the substation l, to ground. Relay 23 functions as a test relay and will not operate unless the ground condition described is encountered. Relay 72 being marginal does not operate at this time. Relay operated locks by way of its inner right hand armature and front contact, and armature 49 of relay 25 to ground.

The operation of the secondary magnet 36 opens the locking circuit for the marginal relay 38 which releases, in turn releasing the secondary magnet 36. Relay 37 being slow to releasedoes not release during brief interruptions of its circuit.

Testing f0? an idle trunk.

ing ground to the test terminal corresponding to the terminal 32. Under these circumstances, a circuit is closed to reoperate relay 38. This circuit may be traced under control of the off-normal contact springs ON, armature and back contact of the secondary magnet 36, normal contacts of the eleventh rotary step sprin s, normal contact and armature of relay 14, brush 22, terminal corresponding to 32 to ground. Marginal relay 38 reoperates over the circuit traced and locks, as previously described, thus closing the circuit previously described to operate the secondary magnet 36 in series with the relay 37. The operation of the secondary magnet 36 opens the locking circuit for the marginal relay 38, which releases, in turn, opening the operating circuit for the secondary magnet 36 and relay 37 in series. The operation of the secondary magnet 36 likewise advances the brushes 20, 21, and 22 another step in accordance with the secondary movement of the selector switch S-1. This cycle of operation continues until an idle trunk is found.

We will assume the idle trunk to be the one associated with the selector switch S2, in which vcase terminal 32 will be free from ground. \Vith the brushes 2), 21, and 22 resting upon the terminals 30, 31, and 32, respectively, of the selector switch S2, terminal 32 being ungrounded, a circuit is closed to operate relay 14 is series with marginal relay 38. This circuit may be traced from battery through the winding of relay 38, through the oft-normal contact spring ON, armature and back contact of the secondary magnet 36, normal contacts of the eleventh rotary step springs, winding of relay 14 to ground at armature 49 of relay 25. It should be observed that while the brush 22 was passing over the terminals of busy lines. the ground encountered on these terminals short circuited the winding of the relay 14, but when an idle trunk is encountered the absence of ground on the test terminal 32 permits relay 14 to operate in series with relay 38. Relay 38, which is marginal, will not operate at this time due to the high resistance of the winding of relay 14 in series with it. The operation of relay 14 extends the connection to the selector switch S2 and a circuit is now closed to operate the impulse relay 28 in series with the polarized relay 13 and the line loop of the calling substation 1. Relay 28 operates over this circuit, closing an obvious circuit to operate slow-to-release relay 29, thus connecting ground to the test terminal 32, thence by way of brush 22 to the lower inner armature and front contact of relay 14. The operation of relay 14 disconnects the impulse relay 24 of the selector switch S1 from the circuit. Relay 24 releases, in turn releasing relay 25, but the latter being slow to release remains operated long enough to permit suflicient time to elapse for relays 28 and to operate and connect ground by way of the test terminal 32 and the brush 22 to the winding of relay 14 before, by the release of relay 25, the operating ground for relay 14 is removed at armature 49 of relay 25.

The selector switch S2 is set in the same general manner as the selector switch S1, except that the impulse relay 28 is employed to operate the switch setting mechanism (not shown). The selector switch S2 is set upon the terminals of an idle connector switch, which we will assume to be the connector switch C, in which case the brushes 40, 41, and 42 come to rest upon the terminals 50, 51, and 52, and the impulse relay 34 of the connector C is operated in series with the loop of the calling substation 1, closing an obvious circuit to operate the slow-to-release relay 39, which connects ground at its armature 47 to" the test. terminal-552 30f the con-'- n c tC; h s P vidi bu y ee wt the test "terminal .52 besides holding ',tl1Q' I I A i interval of time, relay '18 Will release, thus removing ground supplied through the windswitches S41 and TS+2 operated.

5 @Iihe ip l sii d.212M 13 w i h s s ri 4. it t ere fi l ximpnl e e ays 1712 and in sue cession does not operate because :t f w 5 1 rre i t re hi n in j I r ti polarized relay.

The called substation 2'issig'naled in any desired manner'and when the. receiver is I removed atthe called substation 2, a, circuit is closed to operate relay 33. The operation of relay-33 reverses th'e directi on'of the flow ofcurrent in, theloop of the calling substa--- Qdtion lfwhich is in seriesfwith the impulse relay 34. The polarized relayi13 operates on this currentg reversal, clofsin an obvious circuitjto operate relay 12. f fiela'y 12 in turn closes {anjob vious circuit to operate relay 16, which locks junder,controljof relay 18, in ri'es the retardation coil 17 to ground.

'Das enn c Vtthenfthe receiver' isreplaced ,atthe calling substation 1, relay-34: releases, in turnreleasingyelay 39. H Therelease ofrelay'39 reinoves ground irom test terminals 32 and 5 2,

hus Perm tting e ay ,9; e d-2 1w lease. Therel ease of relayl closes a ciricuit to operate the release magnet ofthe i s ectorsw h ;,1thus r storin ebr trod 'it e ee mel..p tie relay19 connectsjthe interrupter 9 in series wi h the n' idin r el y und alm-" of the righ-t hapdinner armature and front contact 10f relay 18 and armature 10 ofrelay';

a ';.R .11 emted e etsb e i proper; polarity through the lamp; .43 .and

\ the. winding {of nyjn in W series, through. P011111 SiC S fih -J OP f the calling subtat in. p z fe elithliereh ot r c' gjd I p' e .--mel aai m o m i d M1 T e. 9 disposal mechanism operates over the circuit described to collect the coin. fIf the fground condition ,tcqntrolled the coin is l prescnt at' the calling substation 1 at this time Lrelay 15 will operate, thus, roviding D aqholding ucircuit for relayi 18. elayyl8 isdmade' slow, to release so that it does not ,but, will ,remain operated [l9 g ,een ghi I relay L5 tooperatea-ndprovidea substitute 5 h ldi ground in the manner described.

Wh n?- b v e vin e t i- 9 1 ounte th i u ated segmentlrel y 11 Wi11" lrelease, removing theT coin collect current ,f jhecalling substation 1,j thus permitting the, .coin mechan sm t res e and r a will be connected to the loop of the calling 1 station 1. Under this condition the absence 10f any tone in the receiver at the substation l e ve t e ere i d rt eu r evi r slid control of the deposi d coi i'whe t e .trr1, pter eg n tee t m t s ae ml ya l w l reiterate,ir q neetmaw n A posal current to the line. Ifthe coin has the proper direction to, operate said Tlie. release ofbeen properly disposed -of,',the absence of ground at the callingsubstation 1 prevents relay 15"fr0m reoperating; hence after an circuit of relay 311 which releases and the circuit is restored to normal.

Ordinary caZZ n0 coin deposited. -Let us assume-thatthe calling substation 1i1nt1atesan ordinary call, that is, a call for which azcharge is imposed, but fails to deposit a coinbet'ore operating thedial at :the calling substation 1.

Under =these circumstances, the circuit functions in .the manner previously described when a coin was deposited. Atthe end of control of relay-37.

No coin having been deposited at the callingsubstation 1, the ground-ordinarily encountered will be absent and consequently the test relay 23 will fail to operate; Under these circumstances, solid ground at the lefthand front contact of-relay25 through the right-hand outer-armature and back contact of the test relay 23 will remain connected to the test'brush 22of; the selector switch S--1. "The presence of this solid ground on-the brush 22 is equivalent to a busy condition upon the-test terminal of every trunk in the group, and the secondary magnet 36 and the marginalrelay 38 will operate in the manner previously describedunder Ordinary call and the brushes 20, 21, and 22 will advance in accordance -with-the secondary movement of the selector switch S1 until -the last rotary step in the drawing vwill be op- .erated, and solid .groundatthe left normal contact ofrelay 23 willbesubstituted for }p r V the groundpreviously supplied through the tle mme ate y when r ay. l O rat 1 winding of the dial tone transformer'DT. During the secondary movement of :the

,switchthe impulse relay 24: will remain oper- 37 to battery. "lvhen the relay 37 releases atthe end ofthe secondary movement of the selector switch S1, ground which is supplied I at the lefthand normal. contact of relay 23 failure to deposit a coin in the coin controlled mechanism.

Under these conditions the receiver will be replaced upon the switchhook of the calling substation 1, permitting the selector switch S1 to release and another call will be initiated in the proper manner.

Free calls.

Let us assume, however, that the calling substation l desires to obtain a connection with a free line, such, for example, as the zero operator. In this event the receiver is removed from the switchhook in the usual way and the dial at the calling station 1 is operated and released in accordance with the code number of the zero operator, which is usually 0. The selector switch S-1 will accordingly be set in accordance with its primary movement upon the proper trunk level which we will assume to be the 10th or O trunk level, of the switch. On this level the brush 46 engages a commutator segment 45 which is connected to conductor 56, thus providing an alternative path to operate the test relay 23 by way of armature 49 and front contact of relay 25 to ground. Relay 23 operated locks in the manner previously described. and seizes an idle trunk in the manner previously described under Ordinary call and the connection is extended to the zero operator, displaying a signal at her position as an indication that a call is in waiting. When the call is answered by the zero operator there is no current reversal in the calling line loop, thus preventing relays 13, 12 and 16 from operating. The failure of relay 16 to operate causes the current supplied to the calling line to dispose of any coin deposited in the coin controlled mechanism to be in a direction to operate the coin disposal magnet in such a manner as to cause the return of the coin.

lVhile for purposes of illustration the brush 46 has been described as establishing a circuit over segment 45 and conductor 56 only on the tenth or zero level of selector S1, it is evident that by multipling the segments corresponding to other levels of the switch bank, the test relay 23 may be arranged so that it will operate on any desired level to enable free calls to be made.

It is also evident that the selector switch S1 may be arranged so as to distinguish between ground supplied by depositing a coin at the calling substation 1, which ground being supplied through the resistance of the coin control mechanism is of comparatively high resistance, and a ground such as may be caused by placing a false signal on the line. This ground is usually of comparatively low resistance. The selector switch may be arranged to meet this condition in any suitable manner. One way The selector switch now tests for of accomplishing this has been illustrated. The marginal relay 7 2 is shown connected in series with the test relay 23 and provided with an armature and front contact wired in parallel with the right hand outer armature and back contact of the test relay 23. Thus, whenever the marginal relay is operated due to the placing of an improper ground signaling condition on the linev of the calling substation 1, the operation of the marginal relay connects ground at its front contact to the test brush 22. The test relay 23 operates as illustrated in the manner already described. A coil 73 of suitable resistance approximately equal to the resistance of the winding of the magnet in the coin controlled mechanism is also inserted in series with the brush 46. It would obviously be necessary for the test relay 23 to be operated and the marginal relay in question to be normal, in order to permit a call to an ordinary line to progress in the proper manner. To obtain this condition on the test relay 23 and the marginal relay referred to, it would be necessary toapply ground of the proper resistance to one c011- ductor of the line of the calling substation 1.

What is claimed is:

1. In a telephone system, calling lines,

each operable to establish various circuit conditions thereon, called lines, classified as charge lines, other called lines classified as free lines, switching mechanism including a selector switch controllable by a calling line to build up a connection to any desired called line, means for preventing said selector switch from functioning in accordance with its normal mode of operation to build up a connection, and means in said selector switch responsive to a particular circuit condition established at the calling station for nullifying the effect of said first means to permit said selector switch to function in accordance with its normal mode of operation to build up a connection to a charge line.

2. In a telephone system, calling lines, each operable to establish various circuit conditions thereon, called lines classified as charge lines, other called lines classified as free lines, switching mechanism including a selector switch controllable by a calling line to build up a connection to any desired called line, means for preventing said selector switch from functioning in accordance with its normal mode of operation to build up a connection, means in said selector switch responsive to a particular circuit condition established at the calling station for nullifying the effect of said first means to permit said selector switch to function in accordance with its normal mode of operation to build up a connection to a charge line, and means in said selector switch operable irrespective of the circuit I for preventing said automatic switches from functioning in accordance with their normal mode of operation'to-build up a connectionil 'andfmeans in one switch iofth e train re sponsive 'to a particular circuit condition established at the" calling station fornullifying-(the effect of said preventing r nea n'sto ermit' said switch to function in' a c- 'cor ance with its normal mode ofoperation to,build up in part a connectiontoa charge." lines 7 v 4. In a telephone system; calling 'line s means "associated With'each calling. line] for establishing i arious circuit 4 conditions thereon, calledlines classified asycha'rgeg lines;#ot-her called lines classified as free lines a train of automatic switches operable under control of a calling linefto buildup. a connection to anydesired called iingmansi for pneventinglsaid automatic switches from functioning in accordance with their normal mode-of operation to buildup 'aconnection l means in one switch ot-the train responsive to a particular circuit condition established: at the calling station fornullifyinguthejef feet-of said preventing} means to permit said sWitcl1-to: function in accordance with its, normal -mode of'operation to build upain parta' connection to a chargeline'yand means in said 'switch operable irrespective of the circuit condition established 'at the calling station 'for permitting said" switch to func-. tion in accordance with its normal mode of opelrationX-tobuild up a connection to a tree line; I

5; Irr'a --telep'hone system," calling 1ines means associated: with each calling ;line for establishing-various circuit conditions thereon; :call'ed ;-lin'es *classified *as charge lines,- othercalled lines classified as free lines, a train of; automatic yswitches operable under control of-thecallringllinerto buildup a con.- nection-wto'; any desired called -linefone of the switches in said switch train having-both a primary and a secondaryfimovement, EIIIBBIIS for *prei'entingw said: last mentioned 7 switch from; functioningdnaccordance with its: nor

' ma l secondary movement; and means in said last mentioned switchQffective at the end of thepnimary morernentthereof responsiye td'a particular? circuit condition established at'i-the cal-ling- {station '-fornullifying :the eff :Eect of'saicl-preventing=means {to initiate the secoridarynnoverheirE- of said I switch raccordancewith its normalmode of operation to buildupinparta connectioii'to a charge Im'ans associatedWvith 'ea'ch'calling linefior est ablishingivarious circuit conditions there-. 0H,; called? .llnes'j' classified as" charge" "linesf other, called linesclas's'ified' as freelines, a

'train' bf automatic switches operable under control ofjth e ball'ing line'tjobuild up a con:-

' nectiibii to desired: called line, one of the I switches insaid switch 'trai'n"havii1g both a rimary secondary movementf means for "pri 'nt fromjunctroning"inaccordance with its nor:

g sa id 'las't'inentione'd switch 5 mill-secondary movement, means in said last I i mentioned switch]effectii eatj'the' end of the primary increment thereof responsive to a particular circuit condition established "at the callingstation ro nullifying" the 'efi'e'ct of preventing gns to initiate the sec f ondary movement of saldswitch in accord"- l ancejwvi'thits normal "mode of operationto build up in parta connection to a'cha rge the end of "the primary movement thereof iris-Spacers of the j circuit "con'diti on eStab lish'ed at'"thscalliiig station "for permitting said switch to function in accordance with a connection to a freline'. 5

7 .j ln a telephone systnijcalling lines, a

coihfco'iitroll ed inecha n'isni associated 'With ea'ch"'callin"g"linef, calledlines classified as lec to r switch fromfunctioning'inaccor'dance' with its. normal 'mode of foper'ation, and means in 'said'istelector switch responsive to the "deposit of "a coin in the coin controlled mechanism '.-'associated with: the "calling line for 'nullif-ying' the "effect" of said first means to: permit said selector switch to operate to buildup a connection toaz charge line.

8.;In a telephone system; calling, lines, a coin' controlled mechanism, associated v With each calling='-.line,- called lines classified as charge lines, otherlca'lled linesclassified as free, lines, swi'tchinginechanism including a selector switch controllable by'a cauing'nns to build up a connection to any desired called=linemeans for preventing said se lector =svtitchl from functioning .in accordance -with sem nar mode' Tof operation; means ins-aid jselector." switch responsive to the deposit-eta coin i n -the coin controlled mechanism; associated jvith' the calling line for nnui-tying she Jefi'ect of sai to-peg'niit said selector switch to'opitate to build up la connectionto a charge'line; and

meansin said.selecEOr' sW'itEh' operable irre' in the coin controlled mechanism for permitting said selector switch to operate to build up a connect-ion to a tree line.

9. In a telephone system, calling lines, a coin controlled mechanism associated with each calling line, called lines classified as charge lines, other called lines classified as free lines, a train of automatic switches operable under control of a calling line to build up a connection to any desired called line, one of the switches in said switch train having both a primary and secondary movement, means for preventing said last mentioned switch from functioning in accordance with its normal secondary movement, means in said last mentioned switch effective at the end of the primary movement thereof responsive to the deposit of a coin in the coin controlled mechanismassociated with the calling line for nullifying the eflect of said firstmeans to initiate the secondary movement of said switch in accordance with its normal mode of operation to build up in part a connection to a charge line, and means in said switch operable irrespective of the presence or absence or a coin in the coin controlled mechanism forinitiating the secondary movement of said switch in accordance with its normal mode of operation to build up a connection to a tree line.

10. In a telephone system, calling lines, a coin controlled mechanism associated with each line, a plurality of groups of trunk circuits, a numerical switch operable under control of a calling line whereby said switch may be set opposite any desired trunk group, called lines classified as charge lines reached via said switch and one of certain of said trunk groups, other called lines classified as free lines reached via said switch and one of the remaining trunk groups, means in said switch responsive to the depositing of a coin in the coin controlled mechanism associated with the calling line for permitting said switch to seize an idle trunk in the trunk group leading to a charge line opposite which group said switch is set, and means in said switch operable. irrespective of the presence or absence of a coin in the coin controlled mechanism. providing said switch is set opposite a trunk group leading to a free line for permitting said switch to seize an idle trunk in said trunk group.

11. In a telephone system, calling lines, a coin controlled mechanism associated with each calling line, a plurality of groups of trunk circuits, a numerical switch operable under controlof the calling line whereby said switch may be set opposite any desired trunk group, called lines classified as charge lines reached via said switch and certain of said trunk groups, other called lines classified as free lines reached via said switch and others of said trunk groups, a relay in said switch operable responsive to the deposit of a coin in the coin controlled mechanism associated with the calling line for permitting said switch to seize an idle trunk in the trunk group leading to a charge line opposite which group said switch is set, and means responsive to the setting of said switch opposite a trunk group leading to a tree line for permitting said switch to seize an idle trunk in said trunk group.

12. In a telephone system, calling lines, a coin controlled mechanism: associated with each calling line, a plurality of groups of trunk circuits, a numericalswitch having a primary and a secondary movement operable under control otthe calling line whereby said switch may be set in accordance with its primary movement opposite any desired trunk group, called lines classified as charge lines reached via said switch and one of certain of said trunk groups, other called lines classified as free lines reached via said switch and one of the remaining trunk groups, means in said switch responsive to the deposit of a coin in the coin controlled mechanism associated with the calling line for initiating the secondary movement of said switch in accordance with its normal mode of operation whereby an idle trunk in any selected trunk group may be seized, and means responsive to the selection of a trunk group leading to a free line for initiating the secondary movement of said switch irrespective of the presence or absence of a coin in the coin controlled mechanism associated with the calling line.

13. In a telephone system, calling lines, a coin controlled mechanism associated with each calling line, a plurality of groups of trunk circuits, a numerical switch having a group hunting movement followed by a trunk hunting movement operable under control of the calling line and having access to said trunk groups, a non-numerical switch operable responsive to the initiating of a call on a calling line for extending the calling line to said numerical switch, called lines classified as charges lines reached via said numerical switch and one of certain of said trunk groups, other called lines classified. as free lines reached via said numerical switch and one of the remaining trunk groups, means in said numerical switch responsive to the deposit of a coin in the coin controlled mechanism associated with the calling line for initiating the trunk hunting movement of the numerical switch in accordance with its normal mode or operation, and means responsive to the selection of a trunk group leading to a free line for initiating the trunk hunting movement of said numerical switch irrespective of the presence or'absence of a coin in the coin controlled mechanism associated with the calling line, 'a plurality of sources of current capable of being applied to the calling line to dispose of the deposited coin, means responsive to the disconnection of the calling station for causing one of said current sources to be applied to the calling line to dispose of the coin, means for maintaining said non-numerical switch in operative relation with the calling line until the coin has been disposed of, and means effective after the coin has been disposed of for causing said non-numerical switch to release the calling line. v

14. In a telephone system, calling lines, a coin controlled mechanism associated with each calling line, called lines, switching mechanismccontrollable by a calling line to build up a connection to any desired called line, means for preventing said switching mechanism from functioning in accordance with its normal mode of operation, means in said switching mechanism responsive to the deposit of a coin in the coin controlled mechanism associated with the calling line for nullifying the eflect of said first means to permit said switching mechanism to operate to build up a connection to a called line,

and means in said switching mechanism re sponsive to the simulated deposit of a coin to maintain the efiect of said first means.

15. In a telephone system, calling lines, a coin controlled mechanism associated with each calling line, called lines, switching mechanism controllable by a calling line to build up a connection to any desired called line, means for preventing said switching mechanism from functioning in accordance wlth its normal mode of operation, a relay in said switching mechanism operable re- I

Images