US2128442A - Prepayment telephone system - Google Patents

Description

Aug. 30, 1938. H. w. ULRICH 2,128,442

PREPAYMENT TELEPHONE SYSTEM Filed May 19, 1936 2 Sheets-Sheet 1 INVENTOR HM. ULRICH A T TORNE Y J Aug. 30, 1938. H. w. ULRICH 2,128,442

'PREPAYMENT TELEPHONE SYSTEM I I Filed May 19, 1936 2 Sheets-Sheet 2 TIM/N G CIRCUIT L." l i IN l/ENTOR H. W UL RICH FIG. 2

A T'TORNEV Patented Aug. 30, 1938 UNITED STATES PATENT OFFIQE Telephone Laboratories, Incorporated,

New

York, N. Y., a corporation of New York Application May 19,

I 9 Claims.

This invention relates to'an arrangement for telephone subscribers switchboards designed to automatically test prepayment coin box subscribers lines .in order to detect fraudulent attempts to obtain service without depositing the required coin.

In a copending application Serial No. 35,226 filed August 8, 1935 for Anderson et al. which makes reference to an earlier filed application Serial No. 8,588 filed February 28, 1935 for Henry Hovland, a system is described having in brief, the following features:

A. A lamp signal common to the operators position which is steadily lighted when the operator actuates a key associated with one of her cord circuits for the purpose of disposing a coin at a subscribers station, which lamp is automatically caused to flash in case no ground is encountered on the line when the coin disposal current is first applied tothe line or when a ground is present on the line at the time of the first application of current which is not caused to disappear thereby.

B. A second lamp signal is caused to flash in unison with the first lamp in the latter case, i. e. when the ground persists on the line after the first application of disposal current.

C. A tone test key which is operated in conjunction with the talk key of the cord prior to operation of the coin disposal key will cause a characteristic tone to be heard in the operators receiver if ground is present on the line at the time which normally may be construed as indicating that the subscriber has deposited a coin in the box.

D. A guard lamp individual to the cord circuit is lighted each time the cord is plugged into an out trunk jack or called line and remains lighted until the. operator actuates the coin disposal key associated with that cord.

E. Substitution of a non-grounded source of talking current for the usual grounded central office battery when a coin disposal key is operated which source remains connected to the calling line in place of the centraloflice battery during the period coin potential is being applied to the line.

The present invention is an improvement on the arrangement described in the before-men- 50 tioned Anderson et al. application in that certain modifications, changes and additions, dictated by experimental use of the original arrangement have been made to render the system more efiicient and satisfactory from a service standpoint.

One object of the present invention therefore 1936, Serial No. 80,522

is to give the operator a beat indication if the coin, which may be in the box, is not disposed of due to failure of the disposal mechanism at the subscribers station on the first application of coin disposal current, but to prevent its being 5 disposed of by a second current application thereby making it possible for the operator after challenging the subscriber to initiate a second cycle of test current application which usually should dispose of the coin thus doing no injustice to the subscriber.

Another object is to reduce the number of signal lamps required for a position.

Another object is to prevent interference with the automatic test operation, when once started, by the accidental operation of a coin disposal key associated with another cord circuit from that over which the test is being made.

Still another.- object is to prevent the repetition of a test cycle on the same line in case the operator holds the coin disposal key operated for a longer interval than it takes the test' circuit to complete one cycle.

A further object is to prevent a beat indication in case a cord circuit is plugged into a line having a call counting device connected in the sleeve circuit and the operator actuates one of the coin disposal keys, which key is arranged tocontrol the call counter on such a connection, as well as to transmit coin disposal current on coin box'lines.

A still'further object is to give the operator a visual indication of the progress of a second test cycle initiated at some later time during the progress of a call, as for example, the collection of a coin deposited for overtime.

A feature of the invention whereby the first object is attained resides in reducing the voltage of the second and succeeding impulses of the test cycle from the high voltage sufficient to actuate the coin disposal mechanism at the station to a value which isrineffective to dispose of the coin if it was not disposed of by the first or high voltage impulse, but which is still Sllfficient to give a beat indication.

A feature in accordance with the second object resides in the elimination of the two common or position lamp signals employed in the Anderson et al. arrangement referred to, and the utilization of the individual guard lamp per 5 cord of that arrangement which serves the threefold purpose of a guard lamp which lights as soon as the calling plug is inserted in the out jack and remains steadily lighted until the coin disposal key is operated and also which flashes 55 either when no ground is encountered on the line by the first application of coin disposal current or when ground persists after the first impulse is applied and until the second impulse is transmitted.

A feature whereby the third object is attained resides in an arrangement whereby when the position circuit has been started the common lead from all cord circuits to the position circuit is opened and is not reclosed until the test cycle has been completed thereby preventing interference with the operation of the position circuit in case a coin disposal key of another cord should be operated during the test cycle then in progress.

A further feature whereby the fourth object is attained resides in preventing the position circuit from completely restoring to normal as long as the coin collect key remains operated thereby making it necessary to release the operated disposal key in order to enable all the position relays to restore in readiness for the start of a new cycle.

A feature whereby the fifth object is attained resides in extinguishing the coin disposal lamp when a message register operates in response to operation of a coin disposal key arranged for the dual function of coin control and message register operation.

A feature whereby the sixth object is attained resides in causing the coin disposal lamp to relight in response to reoperation of a coin disposal key at any time after the first test cycle has been completed and before the called line has been disconnected, after which it is extinguished or fiashed in the same manner as in the case of the first test cycle.

The invention will be understood from the following description when read in connection with the accompanying drawings:

Fig. l of which shows, at the left, two calling subscribers lines, one commonly known as a message rate line, i. e. one equipped at the central oifice end with an electromagnetic message register or counter adapted to be operated by the operator, once for each completed connection, and the other line equipped at the subscribers station with a coin box of the usual prepayment type and at the right of Fig. 1, a called subscribers line. The remainder of Fig. 1 together with Fig. 2 represents an operators cord circuit and the necessary positional equipment arranged in accordance with the present invention to establish a conversational connection between either of the calling stations and the called station.

A detail description of the operation of the circuit arrangement shown on the drawings follows:

COIN Box LINE OALLs It will first be assumed that the coin box subscriber A, shown at the left of Fig. 1, desires to be connected with a called subscriber B, shown at the right of Fig. 1.

By one well-known arrangement for coil box lines, the line circuit at the central oifice may be so arranged as to necessitate the deposit of a coin in the box at the calling subscribers station in order to attract the attention of the operator which method we may call the nickel first method, or, by another well-known arrangement of the line circuit, it may only be necessary for the subscriber to lift his receiver from the hook to display the line lamp at the central oifice, a coin being deposited later, at the request of the operator, which is usually referred to as the nickel last method. Such coin box lines usually have this line lamp at the switchboard colored in some distinctive fashion to warn the operator that such lines require some prescribed action, and special attention, in order to insure payment for each completed connection.

The above-referred to nickel last method, which is the one most commonly used for subscribers coin box lines, as above stated, necessitates that the operator request the subscriber to deposit a coin immediately following his giving the number of the wanted line, which coin is then collected by the operator as soon as the called subscriber answers.

In order that fraudulent attempts to avoid payment by grounding the line in some other manner than by a coin, certain features of the invention, for detecting such fradulent practices, are resorted to and hereinafter described.

Assuming that the line circuit I is arranged on a nickel last basis, as soon as the operator notes the lighted line lamp, not shown, she inserts plug 2 of her cord circuit into jack 3 and inquires the number of the wanted line and immediately thereafter requests the subscriber to deposit a coin, usually a nickel.

Tone test for ground The operator then proceeds to make the usual click test of the called line for a busy condition, by touching the tip of the plug to the line jack, and at the same time tests the calling line for coin ground by operating the detector key D associated with the cord (the talking key T remaining operated). A circuit can now be traced from battery, contacts 5 of relay 4, contacts 6 of relay '1, winding of relay 8, contacts of the detector key D and talk key T, normal contacts of the coin return key R and the winding of the cord circuit relay 9 to ground. Relays 8 and 9 operate in this circuit.

Relay 9 in operating, first closes its inner contacts l5 and I6 thereby connecting the auxiliary battery H, in parallel with the regular cord circuit battery l8, between the left-hand windings of the cord circuit repeating coil I9. The complete attraction of the inner left and right armatures of relay 9 thereafter opens the contacts 20 and 2| thereby disconnecting the regular battery l8 from the cord and leaving the auxiliary battery I! connected in its place.

With relays 8 and 9 operated a circuit is closed to operate relay l2 which can be traced from battery, contacts l3 of relay 8, winding of relay l2, contacts l4 and the winding of relay 9 to ground.

The operation of relay 8 also opens its contacts thereby removing a parallel path around the contacts I] of relay I2. This is to insure that the positional ground 22 is removed from the auxiliary battery I! after relay 9 has operated and that it will be reconnected before relay 9 is finally released. With relays 8 and I2 released, two paths are provided for the positional ground 22 to auxiliary battery 11, one of which paths can be traced from ground 22, contacts 23 of relay 4, conductor 24 and contacts H] of relay 8 to the positive pole of battery I1, and the other path may be traced from ground, contacts 23, contacts H of relay [2 and conductor 25 to the battery IT. The operation of relay 8 opens its contacts l0 and interrupts first path from ground 22 to battery H, but the second path is not opened until relay l2 operates to open its contacts I I.

It will be further noted that ground is not re- 'moved'from the upper left windingof repeating coil I9 until relay 9 has completely attracted its inner left. armature. From the foregoing it will be obvious that the sequence of operations is as follows: First, when relay 9 initially closes its contacts I5 and I6, battery H, which is still grounded over contacts II of relay I2, is connected in parallel with the cord circuit battery'l8 across the cord by way of conductors 26 and 21. Second, when relay 9 is fully operated, its contacts 29 are opened and relay I2 operates to open its contacts II thereby finally removing the last ground connection to battery I! and therefore this battery is now ungrounded and connected across the cord in place of battery I8.

Relay I2v in operating also opens its contacts 28 thereby removing battery from the windings of relays 29 and which will prevent these relays from operating in case a coin key such as R or C in another cord should be operated while the present coin test is being made.

Relay I2 also closes its contacts 3I which connects relay 32-to the tip conductor of the cord over a circuit which can be traced from the tip windingof repeating coil I9, conductor 26, contacts I5 of relay 9, contacts 3| of relay I2, contacts 33 of relay 8, resistance 34 and winding of relay 32 to battery, and further, relay I2 energizes slow operate relay 35 in a circuit which can be traced from battery, resistance 36, inner right contact of relay I2 and winding of relay 35 to ground. Slow relay 35 finally operates and at its outer right contact removes the shunt from the winding of relay 32 which, until this time has prevented relay 32 from operating. Now, if ground is present on the line, which for the present may be assumed to indicate the presence of coin in the box at the subscri-bers'station, relay 32 will operate over the circuitpreviously traced from the tip of the line, conductor 26 and contacts of relays 9, I2 and 8. The operation of relay 32 connects atits right-hand contact the tone source 31 to the operators telephone set coil 38 in an obvious circuit including theouter left back contact of relay 39. Upon hearing the tone in her receiver the operator releases the key D which in turn releases relays 8, 9, I2, 35. and32.

If no ground is present on the line, relay 32 will not operate and no tone will be heard by the operator who will then challenge the calling subscriber and request payment before completing the establishment of the desired connection.

Operator plugs up called Zine Assuming that a ground is, now present on the line the operator proceeds to extend the calling line by plugging the other end of the cord circuit into the called subscribers line jack 40 and rings the called subscriber by means of the ringing key 4|.

Collecting the coin The foregoing test may also be made by the operator while she is receiving the details of the wanted connection, and if she receives the tone signal it will obviously not be necessary to request the deposit of a coin. As soon as the called subscriber answers, as indicated by the illumination of supervisory lamp 42,'the operator proceeds to collect the coin in the calling subscribers box by operating the coin collect key C thereby completing the following circuit for again operating relay 9 and also relay 29: Ground, winding of relay 9, normal contacts of key R and the righthand closed. contacts of key C, right back contact of relay I,- winding'of relay 29 and contacts 28 .of

relay I2 to battery. Operation of relay 29 closes a locking path for itself and relay 9 which can be traced from ground, winding and contact I4 of relay 9, contacts 49 of relay 46', winding of relay 59, contacts 5|. and winding of relay 29- and contacts 28 of relay I2 to battery which circuit is not effective, however, to operate relay 59 until the key C is restored. Relay 29 also completes an obvious circuit for operating the collect register 44. With both relays 9 and 29 operated a circuit is closed to operate relay 4 which can be traced from battery, winding of relay 4, outer right contact of relay 9, contacts 45 of relay 461130 ground at contacts 4'! of relay 29. Relay 4 closesits contacts 56 to operate relay 6'! provided the timing interrupter circuit (shown in the lower left corner of Fig. 2) is not operating for another position. This circuit can be traced from battery, contacts 96 of relay 4, winding and contacts 68 of relay 61 to ground at the right back contact of relay 63. Relay 9'! locks up over its contacts 69 in the following circuit: Battery, contacts 66 of relay 4, winding and contacts 69 of relay 61, contacts 45 of relay46 and contacts 41 of relay 29 to ground.

Operation of relay 9 also disconnects the cord circuit battery I8 from the cord and substitutes the auxiliary battery I! therefor which, prior to operation of relay 4, is connected to ground 22 at contacts 23 of relay 4, but when relay 4 operates and opens its contacts 23, ground 22 is disconnected from battery I], and the tip of the cord. Further, operation of relay 4 closes, at its inner right contacts, an obvious circuit to operate relay 48 which relay in operating closes, at its righthand contact, a path in shunt to contact 49 of the release relay 46, which contacts are included in the previously traced locking circuits for relays 9 and 29.

When key C is released (it only being necessary to operate this key momentarily) the short circult is removed from relay 59 and this relay now operates in the previously traced locking path for relays 9 and 29. 1

Relay 50 operates relay I in an obvious circuit which relay opens its contacts 52 and 53. and closes contacts 54 and 55 thereby disconnecting conductors 51 and 58 from relays 38 and 29, respectively, and connects these conductors together, through resistance 56, to ground at relay 50.

When relay 4 operated it also connected ground at its contacts 59 to lead 60 extending to the timing circuit, shown at the lower left corner of Fig. 2, which causes polarized relay 6! to operate, after a short interval of the order of .2 second depending on the capacity of condenser 62. t The circuit for operating relay 6 I can be traced from ground, contacts 59 of relay 4, conductor 69, outer left contact of relay 63, resistance 94, right-hand winding of relay BI and resistance to battery. During the time required for condenser 62 to become charged, the left-hand winding of relay GI will also be energized and will oppose the righthand winding thereby preventing the relay from operating until the condenser is charged at which time the current in the left-hand winding will decrease to zero and the relay will operate. When relay 6| operates it closes a circuit to operate relay 63 in a circuit which can be traced from ground, contacts 59 of relay 4, contacts of relay SI and winding of relay 63 to battery. Relay 63 in operating, opens its left-hand back contact and interrupts the operating circuit of relay 8| which after an interval releases, depending on the time required for condenser 92 to discharge through the left-hand winding. Therefore, relays BI and 63 will alternately operate and release approximately 2 to 2 /2 times per second as long as relay 4 remains operated.

Relay 63 in closing its inner right contact, completes a circuit to operate relay H which can be traced from ground, inner right contact of relay 63, contacts 12 of relay 61, contacts 13 and winding of relay 1! and resistance 14 to battery. Relay 1| in operating closes its locking contacts 15 to hold itself operated to ground at the left contacts of relay 48 and also connects at its contacts 8 I, the negative coin battery 43 (110 volts) to the tip of the cord and line over the following circuit, battery 43, contacts 19 of relay 29, contacts 11 of relay 30, winding of relay 18, contacts 19 of relay 89, contacts 8! of relay 1|, contacts 82 of relay 39, contacts 83 of relay 46, contacts l5 of relay 9 and conductor 26 of the tip winding of repeating coil 19 and thence to the tip of the line and the subscribers station where the circuit passes through the winding of coin magnet 84 to ground at contacts 85 which contacts are closed if a coin 86 is in the box. Further, when relay 1| energizes an operating path for relay 81 is closed at contacts 15 but this relay is shunted by ground at the inner right contacts of relay 63 over contacts 12 of relay 91 and its own outer left contacts.

As the timing interrupter circuit continues to function relay 5| soon releases thereby opening the energizing circuit for relay 93 which releases and opens its inner right contact thereby removing the shunt circuit from relay 81 which relay then operates in a circuit from ground, lefthand contacts of relay 48, contacts 15 of relay 1!, winding of relay 81 and resistance 88 to battery.

Relay 81 in operating closes its contacts 89, a shunt path around the contacts 8! of relay 1i and contacts 82 of relay 39 in the before traced path for coin battery 43 to the tip of the line.

In case a coin condition exists on the tip of the line, i. e., ground is present, relay 18 will operate in the previously traced coin battery circuit and short-circuit the left-hand winding of relay 99 which relay was conditioned for operation by the closure of contacts 91 of relay 81 when that relay operated. Relay 99, therefore, is prevented from operating if ground exists on the tip of the line when the first impulse of coin battery is applied to the line, i. e., if relay 18 operates.

When the timing circuit relays 8i and 63 operate the second time, relay 63 short-circuits relay 1! which releases. This circuit can be traced from ground, right front contact of relay 33, contacts 12 of relay 31, contacts 92 of relay 81 to the lower terminal of the winding of relay 1|. As the upper terminal of this relay is also connected to ground over its contacts 15 it therefore releases. Relay 81, however, is held operated, when relay 1! releases, over contacts 13 of relay 1|, contacts 12 of relay 91 and front contacts of relay 63 to ground. Relay 1| in releasing opens, at contacts 81, the initially traced circuit for the coin battery 43 to the tip of the line but this circuit is maintained over contacts 89 of relay 81 which relay is held operated.

When relay 1! released and relay 81 operated, a circuit was closed to operate relay 39 which can be traced from ground, outer left back contacts of relay 1|, contacts 93 of relay 81, contacts 94 of relay 88 and winding of relay 39 to battery. Relay 39 opens, at its contacts 82, another point in the initially traced circuit for the coin battery 43 to the line but this battery still remains connected to the line over contacts 89 of the operated relay 81 which contacts shunt both'contacts 8| of relay 1! and contacts 82 of relay 39. Relay 39 in operating closes its contact 95 thereby connecting ground to the upper terminal of relay 8!) thus short-circuiting it, the lower terminal of this relay being also connected to ground at its contacts 94.

When the timing circuit relays 6i and 63 release for the second time the release of relay 63 opens the holding circuit of relay 81 which relay releases and breaks its contacts 93 which disconnects ground from contacts 94 of relay 9!], and the lower winding terminal of relay 80 and from the winding of relay 39. Relay 39 does not release as it now holds operated in series with relay 83, which operates, in a circuit traced from battery, winding of relays 39 and 80, contacts 95 of relay 39 and the left-hand front contacts of relay 48. Relay 81 in releasing also opens at its contacts 89 the circuit for the coin battery 43 to the line which has now been connected to the line for about six-tenths of a second.

When relay 80 operated it opened its contacts 19 and closed its contacts 96 thereby preparing a secondary coin test circuit for connecting battery 91 (approximately 50 volts) to the tip of the line in place of the higher 110 volts) voltage battery 43 which circuit is, however, open at contacts 89 of relay 81. The reason for making the secondary coin test with a lower voltage battery is outlined in the hereinbefore mentioned first object and feature of the invention.

On the third closure of timing relays 6| and 63 relay 1! again operates but performs no function other than to prepare the circuit to operate relay 81 when relay 63 releases.

When relays GI and 63 release relay 81 again operates which closes the previously prepared test circuit from battery 91 to the tip of the line which can be traced from battery 91, winding of relay 32, resistance 34, contacts 96 of relay 99, contacts 89 of relay 81, contacts 83 of relay 46, contacts l5 of relay 9 (Fig. 1) and conductor 26 to the tip of the line. This second test is applied approximately four-tenths of a second after the first test impulse is discontinued.

When relay 80 operated it also closed its contacts 98 thereby preparing a circuit to operate slow relay 35. When relay 35 operates, after a short delay, it short-circuits the resistance 34 thereby connecting the full potential of battery 91 through relay 32 to the line.

Prior to operation of relay35, relay 32 is shunted at the right back contact of relay 35 and hence cannot operate until relay 35 operates even 5 though ground is still present on the line which will be discussed later on.

Relay 35 in operating also closes its outer left contact, thereby connecting ground over contacts 99 of relay I99 to the open contacts I91 of relay 99, thereby preparing a circuit to operate the beat register 102.

Now, if the coin condition (ground) was removed from the line, in the usual manner immediately following the cessation of the first test impulse, relay 32 will not operate under the second test condition.

On the fourth closed period of relay 63 relay 1| releases whereupon it closes its left-hand back contacts and completes a previously prepared circuit to operate the release relay 49 which can be traced from ground, left back contact of relay 1|, contacts 93 of relay 81, contacts I33 of relay 35 and winding of relay 46 to battery, which relay (46) operates and locks up over its contacts I94 to ground at contacts 41 of relay'29, opens, at its contacts 45, the connection between battery9l and. the line, and also opens the circuit of relays 4 and 61 which thereupon release and completes a circuit to operate the coin disposal relay I'il'I which extinguishes the guard lamp I98 (Fig. l) which was lighted when the calling plug was inserted in the called line jack 4 by virtue of the operation of sleeve relay I95.

Relay I91 in operating locks up over its contacts to ground on the sleeve relay I95.

It will be noted that, as before mentioned, the guard lamp I98 was lighted as soon as the cord circuit was connected to the called line and was not extinguished until after the key was operated and the coin disposal circuit arrangement went through its operation cycle. This lighted lamp insures that the operator does not neglect to dispose of the coin .as it is necessary to operate either key C or R to extinguish it, or discon nect from the called line.

Release of relay 4 reconnects ground 22, by way of conductor 24 and contacts III of relay 8, to the auxiliary battery I! and to the tip of the line, opens its contacts 59 thereby removing ground from relay BI and stopping the interrupter timing circuit and at its inner right con tacts releases relay 48.

The release of relay 48 opens at its right-hand contact the previously traced locking circuit for relays 9 and 29, including relay 50, which relays thereupon release and at its left-hand contacts removes ground to release relays II, 81, 89 and 39.

The release of relay 59 opens the circuit of relay 1 which releases, which completes restoration of the coin disposal circuit to normal.

In case the operator holds collect key C operated during the completecycle of operation of the position coin control circuit, relay 59 will remain short-clrcuited, as previously described, under which condition relays 29, 46 and 9 remain operated under direct control of the collect key C thus preventing the position circuit from going through repeated cycles on prolonged closures of the collect key. When the collect key C is held operated until the cycle is completed and then released, it releases relay 29 which releases relay 46 thereby closing the contact 49 which again prepares the circuit for locking relays 9 and 29 when a key C is again operated and subsequently released and also'closes contact 45 thereby preparing an energizing circuit for relay 4 which, when operated, restarts a second cycle.

In case another collect key at the position is operated after the first key is released but before the present collect cycle is completed, relay 1 will be held operated, after relay 59 releases, over resistance 56, the newly operated collect key and the winding of the cord circuit relay corresponding to relay 9, thus preventing the position from completely restoring to normal. That is to say all keys'must be released for a sufficiently long period to permit the disposal circuit to complete its cycle and restore before a key is again operated to start a new cycle of operation.

In cases where a coin has been collected in the norm-a1 manner causing the guard lamp I98 to be extinguished and it should be necessary to request and collect a second coin as an overtime charge, without disconnecting the cord from the called line, a second operation of the collect key C will initiate a second cycle of operation of the position circuit and when relay 4 operates battery will be connected over contacts II8 of relay 4, left-hand inner normal contacts of relay 39, contacts I24 of relay I99, and the left-hand middle contacts of relay 9 to the upper terminal of relay I91 thereby short-circuiting it and causing its release and the consequent relighting of lamp I98, from which point the circuit functions the same as for the collection of the first coin.

No ground on li'ne when collect key operated In case the calling subscriber has failed to deposit a coin before the collect key 0 is operated,

ground will be absent from the tip of the line and relay I8 will not operate. Therefore, when relay 9T operates in response to the first release of relay 63, the flashing relay 99 will operate in a circuit which can be traced from ground at the outer right contact of relay 39, left-hand winding of relay 99, outer right contacts of relay 89, contacts III. of relay 8'! and resistance 36 to battery. Relay 99 operates in this circuit and locks in an obvious circuit through its right-hand winding to ground at contact 41 of "relay 29. At its contacts I9I, relay 99 closes the previously prepared circuit to operate the beat register I92 from ground at the outer left contact of relay 35. At its contact I99, relay 99 disconnects battery, supplied at the right-hand contacts of relay fil, from the upper terminal of relay I96, thereby removing the short-circuit from this relay and, at contacts II9, relay 99 connects the outer left armature of relay 46 to the same relay (I96). When the circuit has completed its cycle, release relay 46 operates as before described to restore the circuit to normal. The operation of relay 46 closes its outer left contact, thereby connecting ground through resistance III to relay I96 which now operates. Relay I96 in operating opens its outer right normal contacts thereby removing the steady ground from guard lamp I98 and at contact 'I'I2 it connects lamp I99 to ground throughthe back contacts of relay H3 and winding of relay H4 which operates, thereby connecting the grounded interrupter H to the winding of relay II3 which alternately operates and releases once per second. Relay I 96 in operating locks itself to ground at sleeve relay I95, therefore lamp I98 will continue to flash, as an indication of a non-standard condition at the subscribers station, until the operator removes the plug from the called line jack 49 which unlocks relay I96.

Ground persists on line after first impulse is terminated If ground is present on the tip of the line when the first impulse of 110 volt battery is connected, and still persists-when relay 35 operates following the third release of the timing circuit (relay 63), relay 32 operates in series with the 50 volt battery 91 to the ground at the subscribers station thereby closing a. circuit to operate the flashing relay 99 which can be traced from ground at the right back contact of relay 39, left-hand winding of relay 99, left-hand contact of relay 32, contact III of relay I39 and contact I I8 of relay 4 to battery. Relay 99 locks up, as before, over its right-hand winding, inner right contact and contact 4'! of relay 29 to ground and when the collect cycle has been completed and the release relay 46 retracts its armature, relay I96 operates to transfer the guard lamp I98 to ground through the winding of relay I I4 over the contact of relay II3 whereupon lamp I98 flashes. as before independent of the rest of the position circuit, which is now restored,until the operator withdraws the plug from jack d0. This flashing lamp, as before, is an indication of a non-standard condition at the subscribers station and requires the operators attention.

In this last case mentioned, 1. e., if ground persists after the first impulse is disconnected, the circuit of the 50 volt battery 97 to the line includes the winding of relay i8 as in the case when the 110 volt battery i3 is connected, but in this latter case relay it, which is marginal does not reoperate on the lower potential of battery Bl which is the same condition encountered in nor mal operation when the ground disappeared following the discontinuance of the first impulse of 110 volt battery. The reason for reducing the potential of the second test impulse, as referred to earlier in the specification, is to prevent collection of a coin which, due to some faulty condition of the coin box, was not disposed of when the first impulse was transmitted.

In either of the foregoing unstandard conditions indicated by flashing of lamp H38, the operator will disconnect the called line and challenge the subscriber requesting him to deposit a coin. If he had not done so originally he will do so now and the operator will again plug up the called line and reoperate key C whereupon the circuit will go through a second cycle, the first 110 volt impulse of which should then dispose of the ground and extinguish lamp its.

If the subscribers coin box is sluggish or for some other reason does not release the coin at the end of the first impulse, or if the subscriber has fraudulently grounded the line at his station to simulate the coin ground, which ground, obviously, will not be removed by the 110 volt impulse, this condition. will also be indicated by the fiashing of lamp Hi8 and the operator will, as before, disconnect the called line and challenge the subscriber. If the subscriber insists he has deposited a coin and the lamp Hi8 again flashes at the end of the second test cycle, the operator will report the line as out of order and, depending on the circumstances, will either refuse the subscribers service or establish the desired connection without further discussion. If the ground at the station was fraudulently connected, the subscriber will, generally, remove it at once upon being challenged and either deposit a coin, which will then be collected in the manner herein described or will abandon the call.

Returning the coin If for any reason. the operator desires to return a deposited coin to the calling subscriber, the return key R is operated which operates relays 9 and 30 in the following circuit, ground, winding of relay 9, left contacts of key R, contact 52 of relay 7, winding of relay 3b, to battery at contacts 28 of relay I2.

The operation of relay 3B prepares, at its contacts l 89, a circuit for connecting the positive 110 volt coin battery IN to the line, which circuit, however, is not completed until the first closed period of the timing circuit, and relay ll operates. Relay 30 also, in closing its locking contact l2l, locks up in series with relays 9 and 50 in a circuit which can be traced from ground, winding and contact M of relay 9, contact 38 of relay 46, winding of relay contact l2! and the winding of relay 30 and contact 28 of relay ii to battery. Relay 55] operates in this circuit and closes its contacts thereby operating relay l which, in operating, disconnects conductors 57 and 58 from the position circuit and connects them together through resistance 56 to ground at relay 50.

Relay 3!], in operating, also operates relay 4 in a circuit which can be traced from ground, contacts I22 of relay 30, contacts 55 of relay 46, contacts I23 of relay 9 and winding of relay 4 to battery. Further the operation of relay 39 removes ground at its outer right contact from the left-hand winding of the flashing relay 9! thereby preventing this relay from operating under the return coin condition. The operation of relay i closes a circuit to operate relay S'l which in operating locks up over its contact 68 and the contacts 65 of relay 66 to ground at contacts of relay 3i]. Relay 6i in operating short-circuits 'relay I86.

Relay l also closes an obvious circuit to operate relay 38 and closes, at its contact 59, a circuit to energize relay E! in the timing circuit, which timing circuit then functions in the before-described manner to operate relay ll which closes its contacts st to complete the'previously prepared circuit from positive battery I20 to the line which circuit includes relay l8 which relay will operate if a ground is present on the line. Under the return condition operation of relay 18, however, performs no useful function.

On the first open period of the timing circuit relays, relay Bl operates and on the next closed period of the timing circuit, relay ll releases. With relay 8"! operated and H released, relay 39 operates which closes at its contact 95 a circuit from ground at relay dB to the upper terminal of relay 3i"! which relay, however, cannot operate in series with relay 39, until the ground on its lower terminal is removed by the release of relay Bl which, however, occurs at the end of the second open period of the timing circuit. At this time, however, relay 80 operates in series with relay 39 and the circuit from battery I23 of the line is opened, first at contacts 89 of relay 81. As the coin battery circuit is opened, relay 7% will release, if operated.

Operation of relay 86 operates release relay 46 in a circuit which can be traced from battery, winding of relay 46, inner left contact of relay 8i) and outer right back contacts of relay 29 to ground. Relay 56 looks, over its contacts I84, to ground at contact I22 of relay 30 and at its outer leit contact closes a circuit to operate relay I01, thereby extinguishing guard lamp 18, which lamp as before mentioned was lighted as soon as the calling plug was inserted in jack 40 of the called line.

The circuit for operating relay Nil can be traced from battery, winding of relay H31, lefthand middle contact of relay 9, contact I24 of relay I00, contact [25 of relay 9%, outer left con-- tact of relay 4-6 to ground -through resistance Hi. Relay llil in operating locks up, at its contacts, to the sleeve relay Hi5 thereby preventing lamp 68 from relighting. Relay 46 also stops the timing circuit by opening its contact 59 and releases relays l, El, 48, 30, 50, l and 9. The circuit is then restored to normal.

MEssAcE RATE LINE GALLs It will now be assumed-that the message rate subscriber M shown in the upper left corner of Fig. 1 desires to be connected with subscriber B.

-MR connected to the sleeve circuit-of the line in parallel with the usual sleeve cut-off relay indicated onthe drawings as I21. Therefore, to call, the subscriber merely lifts his receiver from the hook which lights the line lamp (not shown) at the central office, in the usual manner.

As 'in'the case of coin box lines such message rate lines are characteristically indicated by some distinctive coloring of the linelamp which warns the operatorthat some further action is required, on her part, assoon as the connection is completed,in order to register the call on the subscribers line meter.

When the operator notes the lighted line lamp, not shown, she inserts plug 2 in jack I28, inquires the number of the wanted line and proceeds to establish the desired connection by plugging into jack 40, thereby lighting guard lamp I08.

As the operator is aware, by the color of the calling signal, that the line is of the message rate type, no tone test in this case is necessary.

In the case of a message rate line, it is not necessary to register the call at the beginning of the conversation, but due to the fact that the same operator is handling both coin box and message rate lines and the coin box lines require that a coin be-colle'cted at the start of conversation in order to prevent the subscriber from obtaining service without payment,-it is desirable to make it a uniform practice that the operator also register message rate calls at the same stage of the connection as in the case of the coin box line, i. e., as soon as the called subscriber answers. Further, in order to conserve apparatus it is possible, as hereina'fter described to arrange the collect key Cso that it serves a dual purpose, 1. e., either as a coin collect key if the calling line is provided with a coin box or as a message register key if the calling line is equipped with a message counting device or register. Therefore, because of the arrangement of the apparatus and circuits and to simplify operating practice, the operator is instructed to operate key C as soon as the called subscriber answers, 1. e. when the call supervisory lamp 42 is extinguished, in all cases irrespective of the character of the calling line.

In this case we have assumed that the calling line is a message rate line and therefore when the supervisory lamp 42 is extinguished, indicating that the called subscriber has answered, the operator presses key C, this time to operate the call meter or register MR connected to the subscriber line.

When key C is operated the position register I29 operates in series with the line register MR, thereby lighting the message register pilot lamp I30 in parallel with the message register relay I00. Operation of key C also operates relays 9 and 29 as before described in connection with disposal of a coin. When relay 29 operates it completes, at its contact 41, a locking circuit for relay I00 which relay remains locked until the position circuit has gone through its complete cycle and releases relay 29 as described under the condition of no ground on the coin box line.

Relay I00 operated opens its contacts I24 thereby removing the short circuit from relay I0! and closes its contact I3l thereby operating relay I01 which relay opens the circuit of lamp I08 and locks up to the sleeve relay I05. Relay I00 also opens its contact 99 thereby preventing operation of the beat register I02 when relay 90 operates following the first open period of the timing circuit.

Under the condition described, operation of relay I00 prevents lamp I08 from flashing and also prevents the beat register I02 from operating when the position circuit, in passing through its operation cycle, does not find ground on the tip of the line when the coin battery 43 is first connected which is the normal condition in the case of a message rate line.

What is claimed is:

1. In a prepayment coin system for telephone exchanges, calling subscribers stations, a central office, lines connecting said calling stations and central office, called lines, a device at each calling station adapted to connect ground to the line responsive to the insertion of a coin therein, a plurality of link circuits at the central ofiice each adapted to connect one of said calling lines to one of said called lines, automatic means initiated at the central office for periodically transmitting a predetermined plurality of current impulses to a calling line over a connected one of the link circuits to dispose of a deposited coin at the connected station and remove the ground therefrom, a signal device individual to the connected link circuit, and circuit means for controlling said device, said circuit means being adapted to display said device when the link is connected to the called line, to retire the device if the first current impulse encounters ground on the calling line and the second does not, and to alternately retire and display the device at a definite periodic rate either if the first impulse transmitted does not encounter ground or the second impulse does encounter ground.

2. In a prepayment coin system for telephone exchanges, a calling subscribers station and line, a called subscribers line, a central ofiice terminating said lines, a device at the calling station adapted to connect ground to the line responsive to the deposit of a coin therein, a link circuit at the central ofiice adapted to connect said calling and called lines, means initiated at the central ofiice for transmitting current of a predetermined potential to the calling line over said link circuit to dispose of the deposited coin and remove the ground from the line, and a signal lamp and circuit means for controlling said lamp associated with the link circuit said circuit means being adapted to first light said lamp when the link is connected to the called line, to extinguish it on the disposal of the coin at the calling station and relight it in response to the reinitiation of said current transmission means prior to the disconnection of said link from the called line.

3. In a prepayment coin system for telephone exchanges, a calling subscribers station, a central office, a line interconnecting said calling station and central office, called lines, a device at the calling station adapted to connect ground to the line responsive to the deposit of a coin therein, a plurality of link circuits at the central ofiice each being adapted to connect said calling and one of said called lines, switching means individual to each link circuit adapted when operated to initiate periodic application of current impulses of a predetermined potential to the answering end of the respective link circuit and thence to the connected calling line to dispose of said coin at the calling station and to remove ground from the line, and means to prevent the operation of a switching means associated with any other link circuit from affecting the application of current impulses already initiated to a first link circuit.

4. In a prepayment coin system for telephone exchanges, a calling subscribers station, a central ofiice, a line connecting said calling station and the central office, called lines, a device at the calling station adapted to connect ground to the line responsive to the deposit of a coin therein, a link circuit at the central onice adapted to connect said calling and one of said called lines, switching means associated with the link circuit adapted when operated to initiate the periodic application of a predetermined number of current impulses to the link circuit and thence to the line to dispose of the coin at the calling station thereby removing ground from the line, and means for preventing a cyclic repetition of said impulses if the switching means is held operated after said predetermined number of impulses have been transmitted.

5. In a prepayment coin system for telephone exchanges, a central ofiice, prepayment coin box lines terminating thereat, a message rate line also terminating thereat having a call meter associated with the sleeve circuit thereof at the central office, a cord circuit adapted to extend either of said lines to a called line, a signal lamp, and circuit means for controlling said lamp associated with said cord circuit said circuit means being adapted to light said lamp in response to the connection of either of said lines to a called line, a key associated with said cord adapted when operated to initiate means for transmitting impulses of current to said cord circuit and thence to the answered line to control a coin box mechanism if associated therewith and to control the sleeve circuit of the answered line to actuate a call meter if associated therewith, means for causing said lamp to flash at a steady rate in case the cord circuit is connected to a coin box line and no ground is present on the line when the cord circuit key is operated, and means for extinguishing said lamp and preventing its flashing when the call meter in an answered message rate line operates in response to the operation of said cord circuit key.

6. In a prepayment coin system for telephone exchanges, a calling subscribers station, a central office, a line connecting said calling station and central office, called lines, a device at the calling station adapted to connect ground to the line in response to the deposit of a coin therein, a cord circuit at the central ofiice adapted to connect said calling and one of said called lines, a signal lamp and circuit means for controlling said lamp associated with the cord circuit said circuit means being adapted to light said lamp when the cord is connected to the called line, and automatic means initiated at the will of an operator for transmitting a first impulse of current to the cord circuit and thence to the line of sufficient potential to dispose of a deposited coin at the calling station and to remove the ground from the line and to transmit a predetermined number of successive impulses of such reduced potential as to be ineffective to dispose of the coin, which may be present in the device of the calling station after the first impulse is transmitted, to extinguish said lamp if no ground is present on the line when the second and reduced impulse is transmitted and to cause said lamp to flash if the second and reduced impulse encounters ground.

'7. A system in accordance with claim 1, characterized in this that said signal device is adapted to be redisplayed, before said link is disconnected from the called line, in response to a reinitiation of said automatic means and thereafter controlled as described in accordance with the presence and absence of ground on the calling line.

8. In a prepayment coin system, a cord circuit arranged to control a coin box on a calling line, a signal lamp and circuit means for controlling said lamp associated with said cord said circuit means being adapted to light said lamp in response to connection of said cord to a called line and to characteristically indicate the disposal or absence of a coin in said coin box.

9. In a prepayment coin system a calling line equipped with a prepayment coin box, a called line, a cord circuit adapted to interconnect said calling and called lines, means for transmitting current of a predetermined potential to said calling line to control said coin box, and a signal lamp and circuit means for controlling the lamp associated with said cord said circuit means being adapted to light said lamp when the cord circuit is connected to the called line, extinguish it in response to removal of a deposited coin condition on the calling line when said current is initially transmitted and flash it at a predetermined rate if a deposited coin condition is absent when said current is initially transmitted or such a condition is present and persists after said initial transmission.

HORACE W. ULRICH.

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