US1496772A - Pay-station automatic telephone system - Google Patents

Description

June 10 1 924. 1

R. D. CONWAY -PAY5 TI9N AUTOMATIC TELEPHONE sYsf'aM Fi March 17. I *3 Sheets-Sheet 1' hive/#02:. fiay Z7. Con wa y RmmeMm/ June 10, 1924. 1,496,772

R. D. CQNWAY my 'STATIONAUTOMATIG fzysraonz sYsT-sm Filed March 17. 1923 s Sheets-Sheet 5 Awe/#01 /7 0 y [7. Con way Patented June 10, 1924,

' OFFHCE.

ROY D. CONWAY, OF OHATHAM, NEW JERSEY, ASSIGNOR T0 WESTERN ELECTRIC COMPANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK;

PAY-STATION AUTOMATIC TELEPHONE SYSTEM.

Application filed March 17, 1921. Serial No. 452,977.

To all whom it may concern:

Be it known that I, ROY D. CONWAY, a citizen of the United States, residing at Chatham, in the county of Morris, State of New Jersey, have invented certain new and useful Improvements in Pay-Station Automatic Telephone Systems, of which the following is a full, clear, concise, and exact description.

This invention relates to machine switching pay station telephone systems.

The object of the invention 1s to provide an improved coin control circuit arrangement for automatic telephone systems of the type wherein the calling party may either select another subscribers line or an operators position. I

In the circuit arrangementof this invention, if the connection is built up from one automatic station to another automatic station, the disposal of the coin which must be deposited in order to build up the connection, taken care of purely automatically upon the breaking down of the connection, the coin box magnet being selectively operated by positive or negative current from a coin control circuit at the central ofiice to collect or refund the coin depending upon whether or not the called party has answered. hen, however, the calling party builds up a connection to an operators position who then completes the connection, the coin control circuit is cut off and the coin is disposed of by collect or refund current applied to the calling line by the operator. hen the operator removes the plug after disposing of the coin, the automatic switches are released, but if she removes the plug without disposing of the coin, the automatic switches are held set and the calling lamp is again lighted to call her attention to this omission.

Referring to the drawings, Fig. 1 shows a calling line, a line switch and the coin control circuit; Fig. 2 shows a secondary line switch, a first selector, a connector and an automatic station; Fig. 3 shows a trunk terminating at an operators position, and a cord circuit at such position and a manual station.

The invention will be most readily understood from a detailed description of'the operation of the system.

The removal of the receiver at substation A operates the line relay 100 of the welllrnown Keith line switch PLS which closes the circuit of the pull down winding 101 to cause the line switch to plunge and seize the preselected trunk 102, 103, as shown and described for example in-Patent No. 1,304,369 of May 20, 1919 to A. J. Ray. The closure of contact 113 of the primary line switch applies ground to holding conductor 114 lead ing to the pull down winding 200 of the secondary line switch SLS causing such switch to plunge and seize a preselected first selector FS in the well-known manner. This selector may be of the type shown in Reissue Patent No. 13,901 issued April 13, 1915 to F. Newforth, J r. The seizure of this selector causes a ground to be applied to the release wire 201, 115 in the well-known manner.

These two line switches thus have extended the calling line to a first selector. Relay L (Fig. 1) is now operated over the line circuit as follows: free pole of battery, normal contact of relay H, resistance 104, right armature and normal contact of relay NN, inner right armature and normal contact of relay B, normal contact of relay A, trunk conductor 103, including a contact of the line switch, trunk conductor 102 including a contact of the line switch, normal contact of relay A, inner left armature and normal contact of relay B, retardation coil 105, relay L, normal contact and outer left-hand armature of relay NN to ground. If the coin has alreadybeen deposited in the coin box. contact 109 is closed and a ground is applied through the polarized magnet 110 to the calling line, but the resistance of magnet 110 prevents this ground from short-circuiting relay L which is in parallel with said magnet and the circuit characteristics are such that relay L operates. Relay L closes a circuit for relay DD to ground the release wire 107 connected to the holding winding 108 of the lin switch before the circuit of the pull down winding 101 is opened by the release of slow relay 100 after such relay is cut off due to the line switch operating. The circuit for relay DD is as follows: battery left armature and alternate contact of relay L, normal contact of relay M, normal contacts of relays NN and D, relay DD to ground.

The lowermost armature of relay DD applies the ground referred to to the sleeve wire 107. Slowfrelay N also operates in parallel with relay DD and operates relay N N in a circuit including the inner left armature and normal contact of relay IIH. Relay N N in attracting its outer left armature removes the shunt from around resistance 106 for a purpose which will appear. In attracting its inner left armature it opens the original circuit of relay DD andcloses a substitute circuit therefor to hold such relay energized to prevent premature release. Relay N applies ground to the sleeve wire 115. In attracting its right armature relay llN connects relay RT to the ring side R of the line in place of resistance 104. Relay HT is marginal and its function is to test for the presence of a coin in the coin box of the calling station A. This coin box may be of the type shown in Patent No. 1,043,219, issued November 5, 1912, to O. F. Forsberg. The deposit of the coin closed contact 109 to connect the polarized magnet 110 to ground from the tip side of the line as described. lVhen relay NN attracts its outer left armature, removing the short circuit from about resistance 106 and attracts its right armature which substitutes the marginal test relay RT for the resistance 104, the ground applied to the calling line at contact 109 by the deposit of the coin causes the marginal coin test relay RT to operate to place the central oflice stepping circuitunder control of the calling dial to permit the calling party to build up his connection. If the coin is not deposited the contact 109 is not closed and relay RT will not operate, leaving the stepping circuit for th switches disabled. The function :of resistance 106 is to prevent relay RT from operating if the coin has not been deposited. This relay will operate only in case contact 109 has grounded the line and will not operate through relay I1 and resistance 106. The circuit would remain in this condition until either the subscriber deposited a coin or restored his receiver which latter act would cause release of the equip-- ment. Relay ET in operating energizes slow to operate relay S. this circuit including the release wire now grounded at the front contact of relay N. In closing its co.n tact 116 relays locks up to the outer left an mature and normal contact of relay Y. In

attracting its outermost left armature relay S, operates slow relay H, which locks itself in a circuit including the outer right arma-v ture and back contact of relay B, and also operates relay HI-I. Relay HH in attract ing its outer left armature extends the grounded spring 113 to release wire 107 to hold the primary line switch set after relay DD releases and removes the ground applied at the lowermost armature of the relay. In attracting its inner right armature relay 'HH applies a ground to the right of coil 105 in shunt of the relay L and resistance 106 to remove them from the impulse circuit asset/7s zvhich may be traced as follows: free pole of battery, impulse relay R, innermost left armature and front contact of relay S, inner right armature and normal contact of relay B, normal contact of relay A, the calling line circuit, normal contact of relay A, retardation coil 105 to the ground referred to at the inner right armature of relay Ill-l. Relay R closes a bridge to the impulse relay of the first selector FS. This bridge leads from the tip conductor T, retardation coil 117, alternate contact of relay R, outer left armature and normal contact of relay B, relay M, outer right armature and normal contact of relay Y to the ring conductor It.

Relay M operates in this bridge and closes a. holding circuit for slow relay N, before its circuit has been opened by the dcenergization of relay L long enough for it to release, in order to prevent the circuit of relay A from being closed at this time. The seizure of the first selector causes a ground to be placed on release wire 201, 115 in the well-known manner.

The calling party now operates his sender 111 to interrupt the circuit of the impulse relay R. Relay R in turn repeats these impulses to the impulse relay of the first selector FS which in the well-known manner finds an idle connector C which is then set on the called line multiples and the called line is automatically rung. Vl hen the con nector was seized slow relay 20st was operated by relay 203 to ground release wire 206 in the well-known manner. The response of the called subscriber operates relay 202 which reverses the direction of current flow in the calling line supplied through relay 208. Polarized relay l? in the coin control circuit (Fig. 1) thereupon operates whereupon relay E operates and locks up to the grounded conductor 10?. Relay E prepares a circuit from the collect source of positive current 118 which will be closed to collect the coin upon the breaking down of the connection. Relays P and E operate relay .1, the circuit including the outer left armature, and alternate contact of relay E. the outer right armature, and alternate contact of relay Relay A cuts off the bridge containing relay i which releases relay M, the latter releasing slow rela N. The callinglineis now extended through to the connector relay 203. Talking current is fed to the called line through the windingsof relay 202 and to the calling line over a circuit including the free pole of battery, right winding of relay 203, outer armature and alternate contact of relay 202. the upper or tip talking conductor T to the calling line, returning over the lower or ring I conductor R, contact 120 of. relay E, polarized relay P-and its non-inductive shunt, the ring conductor R to ground through the inner armature and alternate contact of relay 202 and the left winding of relay 203. i

lWhen the calling party restores his receiver the connection is released, but the release of the primary line switch PLS is delayed until the coin control circuit of Fig. 1 has functioned to cause the collection of the coin. WVhen the coin is collected this switch is also allowed to release.

When the calling party replaces his receiver, relay 203 releases, releasing the usual slow relay 204 which by energizing the release magnet 205 restores the connector. The retraction of the left armature of slow relay 204. removes ground from the release wire 206 causing the release relays (not shown) at the preceding selectors to deenergize to restore the corresponding selectors.

The relay S is at this time locked to this ground on the release wire and consequently releases when such ground is removed as described. In retracting its intermediate left armature it opens the holding circuit of the secondary line switch SLS thus causing the release of the same in the well-known manner. It will be remembered that when relay S first operated it operated relays H and Relay H then locked itself up in a circuit independent of relay S, including a back contact of rela B and held relay HH operated. Relay H closed a local holding circuit for the primary line switch including the holding winding 108 and contact 121 of such switch, conductor 107, outer left armature and alternate contact of relay HH,c0I1 ductor 122 to grounded spring 113.

The relay S in retracting its outer left armature prepares a circuit for a pick up relay Y which is closed when the interrupting machine 123 closes its upper contact. Relay Y then locks up to grounded conductor 107. Relay Y in attracting its outer left armature prepares a circuit for a coin current applying relay B which is closed when the interrupting machine 123 next closes its lower contact. Relay B in operating closes a circuit to apply collect current of positive polarity from the source 118 to the polarized magnet110 in the coin box, this circuit including the outer right armatures and alternate contacts ofrelays E and Y, the winding of relay M. inner left armature and alternate contact of relay B, normal contact of relay A and the tip side of the line to ground through the coin box magnet 110. Relay A was released when relay S released. The coin box magnet 110 in operating on positive current causes the collection of the coin and the opening of contact 109 as described in said Forsberg patent. When relay B operates from the interrupting machine 123 as described it opens at its outer right armature the locking circuit of slow relay H which is holding relay ,HH operated. The latter relay is maintaining the holding circuit of the line switch closed as described. Before the slow r lay H can deenergize when its locking circuit is opened by relay B another circuit for relay H is closed at the front contact of relay'M in the coin current circuit operated due to relay B operating. When relay B is released by the interrupting machine it again closes the'locking circuit for slow relay H. If the coin is collected by the first impulse the coin ground is removed from the line by the opening of contact 109 and the next time the relay B is operated by the interrupting machine and opens the locking circuit of slow relay H, the other circuit for this relay is not closed since relay M does not operate due to the absence of the coin ground on the tip side of the line. Consequently the slow relay H releases, releasing relay HH which-in retracting its outer left armature opens the holding circuit described for the primary line switch which releases in the well-known manner. Relays E and Y release due to the release of relay HH.

If the called line is busy or the called subscriber fails to answer the polarized relay P would not operate and lock relay E. Upon the operation of relay Y therefore due to the release of relay S when the calling party replaces his receiver, relay Y would connect refund current of negative polarity from the source 119 by way of the outer right armature and back contact of relay E to the call-- ing line, instead of collect current, and the coin would be refunded.

A lamp 125 controlled by relay Y is provided to give a signal by its sustained illumination in case of trouble.

Assuming now that the calling party desired a connection to an operators position. In that case he inserts a coin and dials a certain digit or digits to select a trunk 207, 208, 209 terminating in a. jack 300 at an operators position.

These trunks are shown as terminating in a level of the first selector FS but they may terminate in any selector. \Vhen the trunk 207 208, 209 is seized, relay 301 operates in a circuit including its grounded right wind-- ing, outer left normal contact of relay 302, right normal contact of relay 303, left wind ing of relay 301, inner left normal contact of relay 303 over the tip conductor, retardation coil 117, alternate contact of impulse relay R, relay M, ring side of the line, conductor 30 1 to battery at the middle left armature of relay 303.

the outer right armature and alternate contact of relay S,-and .outer left normal contact of relay E. Relay A cuts off the repeater and connects the calling line through to the tip and ring contacts of the ack 300, relay E not being operated at this time due to the failure of polarized relay P to operate. Thus relay P is excluded from the calling line circuit. When relay 303 operated, it applied ground from the contact 305 of relay 302 to the sleeve or release wire 306 to hold up the release relays (not shown) at the preceding sclectors and the relay S in the coin control circuit just as when the connector C was seized.

' The seizure of the trunk caused a tone to be transmitted from induction coil 309 to the calling line to inform the subscriber that the call is extended to the jack 300, this cincuit including the inner normal contacts of relay 310. The attraction of the middle left armature of relay 303 closed the circuit of the calling lamp 307. The operator now inserts plug 308 into jack 300 but the current flow from the battery in the cord to the calling line is not in the proper direction to operate polarized relay P and therefore relay E remains inert. When the operator inserts plug 303 into ack 300 relay 302 operates, and by closing its inner right contact short circuits the primary winding of induction coil 309, thus removing the tone from the calling line. Class of service tone current from the source 197 associated with the calling line now flows through the primary winding of induction coil 309 to ground at the inner right armature of relay 302, this tone current having been shert circuited at contact 305 up to this time. By induction through the secondary winding of coil 309 this tone is transmitted to the operators head set when she actuates her listening key 312. The operator now actuates key 313 which operates relay 310 the circuit including-the middle left armature and alternate contact of relay 303, a contact of key 313, the tip side of the line to the grounded side of the battery in the cord. In attracting its outer right armature it locks itself so that-it remains energized after key 313 is released. While relay 310 by attracting its inner armatures opens the original class tone circuit to the operators head set, a substitute circuit for transmitting the tone is closed including the confacts of key 313, and thus this tone is not removed until the key is released. Thus the operator can reapply the tone at any time while the plug is inserted by merely operating key The operator now talks with the calling party, learns the number desired, and if a charge is-required instructs him as to the coins to be deposited. As the coins drop into the box they strike gongs which transmit tones to inform the operator of their denominations. The operator then neacym tests the called line jack in the well-known manner, and if idle, inserts the plug and rings over the line. When the called party answers, or at any time thereafter, she actuates collect key 31 1-. current from the source of positive current 315 over both sides of the trunk and calling line in parallel to ground through the polarized magnet 110 in thecoin box to collect the coins. cuit to light lamp 317, and as soon as the key is released the coin box magnet 110 releases and disconnects the coin ground. She again acrnatcs the key and if the lamp does not light it indicates that the coin box magnet has functioned properly and removed the coin ground.

ll hen the calling and called parties replace their receivers the supervisory relays 348, 339 release lighting the, lamps 320, 331 in the well'known manner whereupon the operator removes the plugs. The removal of plug 308 from jack 300 releases relay 302 which in closing its outer left back contact shunts the right winding of relay 30.1, the relay 310 being still locked up. Belay 301 thereupon releases releasing relay 303. Relay 303 in releasing its middle left armature releases relay 310, and in retracting its outer left armature removes ground from the release wire 306 causing the release of the selectors and relay S, Fig. 1. Relay S in retracting its intermediate left armature releases the secondary line switch and .in retracting its outer left armature opens the original circuit of slow relay H. This relay is however locked in a circuit including the outer right normal contact of relay B. Relay Y operated and locked when relay S released as described and connected the interrupting machine to relay B. When therefore this machine operates relay B and opens this locking circuit, no coin ground being present at the substation, relay M fails to operate and no alternative circuit is closed for relay H whereupon it releases as described, releasing relay HH. Relay HH in retracting its outer left armature opens the holding circuit for the primary line switch causing its release.

If the coins for any reason were to be refunded the operator would actuate refund key 318 instead of collect key 314, which causes refund currentof negative polarity to be impressed on the calling line from the current source 319 through relay 330 to operate the polarized relay 110 to refund the coins. Lamp 321 lights upon the second actuation of the key, if the coin box magnet has not operated properly and removed the coin ground.

If the operator removes the plug 308 without actuating either coin key the connection is not released but the calling lamp This impresses collect The relay 316 operates in this cir- J.)

307 is again lighted in the following manner to call her attention to this omission. If she has failed to dispose of the coin when the plug is removed ground is present in the tip side of the line from the coin box and this ground completes a circuit over conductor 322, inner right armature and front contact of relay 310, inner left armature and back contact of relay 302, right armature and front contact of relay 303, left winding of relay 301, innermost left armature and front cont-actof relay 303 to battery. This holds relay 301 which. in turn holds relay 303, the latter holding relay 310. Relay 303 applies battery to lamp 307 over the outer right armature and normal contact of relay 302 which released when the plug was pulled out. Relay 303 in maintaining its outermost left armature attracted holds ground on release wire 306 thus preventing the release of the switches. The operator inserts the plug and disposes of the coin, thus removing the coin ground. Upon the removal of the plug the connection is released as described.

Certain lines called free lines are segregated upon connectors which do not reverse the current flow upon the response of the called party. On a call to such a line the relay A is not operated due to relay P not operating and current is fed to the calling line over the relay R and normal contacts of relay A, the circuit being balanced by a retardation coil 105. The retardation coil 117 in a call of this character prevents shunting of the voice currents. Upon the replacement of the receiver by the calling party the connection is broken down and due to the relay E being in normal condition, the coin control circuit functions to refund the coin exactly as described when the called line was busy.

The discharge of the condensers is prevented from interfering with the character of the impulses transmitted by the impulse relay R to the switches in the following manner. When the relay R is energized due to the deposit of the coinit operates relay D. Relay D operates relay DD. Relay DD connects the condensers to the tip and ring conductors. However, upon the first break in the calling line circuit by the dial relay D releases quickly, releasing relay DD which disconnects thecondensers from outgoing trunk conductors. Relay D is slow to operate as shown and remains inert during the time the armature of relay R is vibrating and only energizes again when the 7 line circuit is closed as the dial reaches its normal position. These condensers are provided to inductively connect the calling and called ends in the case of free calls.

"to preventit from attracting its armatures Relay S is made slow to operate, as shown,

and locking due to possible momentary operation of marginal coin test relay RT under certain conditions at the time it is connected to the ring side of the line in;

and

to selectively operate the coin box magnet to dispose of the coin, means actuated by the disconnection of the connecting circuit from the trunk for releasing the automatic switches, and means for preventing the release of said switches and for again actuating said signal if the operator disconnects the connecting circuit from the trunk without disposing of the coin.

' 2. In a telephone system, the combination with subscribers lines, coin boxes associated therewith having polarized magnets therein,

an operators position, trunks terminating thereat in jacks, automatic switches for extending the calling line to one of said trunks, a calling lamp for said trunk lighted by the seizure thereof, a cord circuit, means actuated by the insertion of the answering plug of the cord circuit into the jack of theseized trunk for extinguishingv said lamp, sources of positive and negative current, .keys in said cord circuit for applying currenttothe calling line to selectively operate the coin boX magnet to collect or refund the coin, means actuated by the withdrawal-of the plug from the jack for releasing the automatic switches, and means for preventingthe release of said switches and for again lighting the calling lamp actuated if the plug is withdrawn before the coin is collected or re funded.

3. In a telephone system, the combination with subscribers lines, coin boxes associated therewith, senders for said lines, automatic numerical and non-numerical switches, operators positions, means actuated by the deposit of a coin for altering the substation coin-box connections, means controlled by the removal of the receiver and the altered coin box connection for placing said sender in operative relation with said numerical switches whereby the subscriber may select a position, a calling lamp lighted thereby, means controlled by the operator for answering the call, means controlled by the operator for collecting or refunding the coin and restoring to normal condition the coin *box connections, and means for preventin the use line,

release of the switches and for again lighting the lamp if the operator disconnects the calling line from her position without restoring to normal condition the coin box. connections. Q

45. In a telephone system, the combination with subscribers lines, coin boxes connected therewith, senders for said lines, automatic non-numerical and numerical switches, op erators positions, means actuated by the tie posit of a coin for grounding one side of the means jointly controlled by said grounded condition and the removal of the receiver for placing said sender in operative relation with said numerical switches whereby the subscriber may select a position, .1 calling lamp lighted thereby, means controlled by the operator for answering the call and extinguishing the lamp, means coir trolled by the operator for collecting or re funding the coin and removing said ground, means actuated by the disconnection of the calling line from the position by the operator for releasing the switches, and means actuated by the presence of said ground when the operator disconnects for preventing the re lease of the switches and again lighting the calling lamp.

5. In a telephone system, the combination with subscribers lines, coin boxes associated therewith, senders for said lines, automatic switches controlled thereby for interconnecting a pair of lines, a coin control circuit at the central ofiice for applying collect or refund current to the calling line automatically to collect or refund a coin upon the breaking down of the connection dependent upon whether or not the called party has an swered, an operators position adapted to be selected by said automatic switches under control of the sender, a calling lamp lighted thereby, meanscontrolled by the selection of said position for rendering said coin control circuit inefiective, and manual means controlled by the operator for collecting or refunding the coin.

6. In a telephone system, the combination with subscribers lines, coin boxes associated therewith, senders with said lines, automatic switches controlled thereby for interconnect ing a pair of lines, a coin control circuit at the central ofiice for applying collect or re fund currenttothe calling line automatically to collect or refund a coin upon the breaking down of the connection dependent upon whether or not the called party has answered, an operators position adapted tobe selected by said automatic switches under control ofthe sender, a calling lamp lighted thereby, means controlled by the selection of said position for rendering said coin control circuit J ineffective, manual means controlled by the operator for collecting or re funding the coin, and means actuated if the operator disconnects without disposing of acey/a the coin for holding the connection to her position and again lighting the calling lamp.

'7. In a telephone system, the combination with subscribers lines, coin boxes associated therewith, senders for said lines, automatic selectors and. connectors for interconnecting said lines, a coin control circuit before the first of said selectors for applying collect or re fund current to the calling line automatically upon the breaking down of the connection dependent upon whether or not the called arty has answered, a repeating relay bridge associated with said coin control circuit actuated by the sender to repeat impulses to said automatic switches to set the same, an operators position selectabl by one of said selectors, means controlled by the selection of the position for cutting off said coin control circuit and said bridge and for cutting the calling line directly through'to the position, and keys controlled by the operator for applyi collect or refund current to the ailing line. I v

8; In a telephone system, the combination with subscribers lines, coin'boxes associated therewith, sendersforsaid lines, a repeating relay bridge at the central o'flice, means con-- trolled by the deposit of a coin for placing the sender in operative relation to said relay whereby the subscriber may build up a connection, a coin control circuit before the first of said selectors for applying collect or refund current to the calling line automatically upon the breaking down of the connection dependent upon whether or not the called party has answered, an operators position, means controlled by the selection of the position for cutting off said coin control. circuit and said bridge and for cutting the calling line directly through to the position, a calling lamp lighted thereby; keys controlled by the operator for applying collect or refund currentto the calling line to operate the coin box magnet to dispose of the coin, and means for preventing the release of the connection and for again lighting the lamp if the operator disconnects without disposing of t-hecoin.

9. In a telephone system, the combination with subscribers lines, coin boxes associated therewith, senders for said lines, a. repeating relay bridge at the central office, means controlled by the deposit of a coin for placing the sender in operative relation with the relay of said bridge whereby the subscriber may build up a connection, an. operators position, means controlled .by the selection of the position for cutting off said coin control circuit and said bridge and for cutting the calling line directly through to the position, a calling lamp lighted thereby, keys controlled by the operator for applying collect or refund current to the calling line to operate the coin box :magnet to dispose of the coin, and means for preventing the release of the connection and for again lighting the lamp if the operator disconnects without disposing of the coin.

10. In a telephone system, the combination with subscribers lines, coin boxes associated therewith senders for said lines, automatic numerical and non-numerical. switches, for interconnecting a pair of lines, a coin control circuit at the central office for applying collect or refund current to the calling line, means actuated by the replacement of the receiver by the calling subscriber for holding the connection to the coin control circuit and releasing the numerical switches and for causing said coin control circuit to apply collect or refund current to the calling line depending upon whether or not the called party has answered, an operators position adapted to be selected by said automatic switches, a calling lamp lighted thereby, means controlled by the selection of said position for rendering said coin control circuit ineffective, and manual means controlled by-the operator for collecting or refunding the coin.

11. In a telephone system, the combination with subscribers lines, coin boxes associated therewith, senders for said lines, primary and secondary line switches and numerical switches for interconnecting a pair of lines, a coin control circuit at the central oflice for applying collect or refund current to the calling line, said coin control circuit being located between said non-numerical switches, means actuated by the replacement of the receiver by the calling subscriber for holding the connection to the coin control circuit and releasing the secondary line switch and numerical switches and for causing said coin control circuit to apply collect or refund current to the calling line depending upon whether or not the called party has answered, an operators position adapted to be selected by said automatic switches, a calling lamp lighted thereby, means controlled'by the selection of said position for rendering said coin control circuit inefl'ective, manual means controlled by the operator for collecting or refunding the coin, and means actuated if the operator disconnects without disposing of the coin for holding the connection to her position and again lighting the calling lamp.

In witness whereof I hereunto subscribe my name this 14 day of March, A. D., 1921.

ROY D. CONWAY.

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