US2248575A - Telephone system - Google Patents

Description

July 8, 1941. v c. E. LOMAX TELEPHONE SYSTEM Filed April 1, 1959 ZQPRE 25o INVENTOR. CLARENCE E. LOMAX ATTORNEY5.

Patented July 8, 1941 TELEPHONE SYSTEM Application April 1, 1939, Serial No. 265,460

21 Claims.

The present invention relates to improved apparatus for providing different classes of service to difierent groups of substations embodied in an automatic telephone system and, more particularly, to improved apparatus for providing, without charge, restricted telephone service to substations of the paystation type.

In certain cases it is desirable that provisions be made whereby certain of the substations'of an automatic telephone system are restricted to calls to substations within certain areas or to predetermined telephone stations. For example, in the case of a system comprising a network of exchanges in two or more closely adjacent cities or towns, it may be desirable to provide unlimited service to certain subscribers who pay a high rate for service or for substations connected for metered service, at the same time restricting other subscribers who pay a lower rate, to local calls within the area of one of the cities. Again, it may be desirable to arrange the system apparatus so that calls originating at paystations may be routed to information operators, fire stations, police stations and the like without coin deposits, while all other connections are only successfully obtained after the correct coin deposits have been made. Various arrangements permitting services of the character just mentioned have been previously developed but the usual arrangements of this type are complicated in character and are of restricted application.

It is an object of the present invention to provide improved telephone apparatus of simple and economical arrangement which is positive and reliable in its operation to provide services of the character briefly outlined above.

It is another object of the invention to provide in conjunction with one or more of the substations of an automatic telephone system improved circuits arranged to restrict efiective operation of the calling devices of the substations to the dialing of directory numbers having not more than a specified number of digits.

It is a further and more specific object of the invention to provide improved apparatus of the character mentioned wherein the restricted operation of the calling devices provided at certain substations cf the system is achieved through the provision of circuit arangements for bloclnng the flow of direct current of one polarity over the lines respectively extending to such substations.

In the illustrated embodiment of the system there is provided one substation which is arranged for restricted service, together with a plurality of lines including one line extending to the substation and a plurality of automatic impulse-responsive switches controllable over the lines to establish connections therebetween. In order to restrict the services available to the above-mentioned substation, there is serially included in the line extending thereto a unidirectional conductive device in the form of a rectifier, which device is so poled that, by virtue of its current blocking characteristic, it prevents current pulses from being transmitted to all but a few of the numerical switches embodied in the system. The device is thus arranged to prevent connections from being routed from the substation through the regular connector switches of the system to at least a portion of the subscribers lines. More particularly, the substation which is arranged for restricted service is of the paystation type and comprises means for receiving coins or the like which includes a coin deposit channel, a coin collect channel and a coin refund channel; together with the usual transmitter, receiver and impulsing device. There is further provided a normally incomplete low impedance path shunting the transmitter, which path is effective, when completed, to render the transmitter ineffective to transmit signal currents over the line extending to the substation. In addition, the substation apparatus includes switching means operative in response to the deposit of a coin in the coin receiving means for short-'circuiting the unidirectional conductive device included in the line, thereby to render this device ineffective to prevent the flow of direct current of either polarity over the line. This switching apparatus further functions to complete the above-mentioned path for short-circuiting the substation transmitter. Additional key operated switching means is provided which, when operated, functions to short-circuit the unidirectional conductive device and to open the above-mentioned low impedance path shunting the transmitter. This additional switching means, when operated, further functions to permit a coin deposited in the coin deposit channel of the coin receiving means to pass into the coin collect channel. By virtue of this arrangement the desired coin collecting operation is performed incident to the completion of a talking connection involving a distant substation of the character requiring a coin deposit in order to route a call thereto. A second key operated switching device is provided for the purpose of obtaining coin refunds when calls originating at the substation are not successfully completed. This second switching device is arranged to interrupt an established loop circuit extending to the substation and has associated therewith a slow-acting device which functions to retard movement thereof from the open circuit position to the closed circuit position, thereby to prevent fraudulent use of the substation.

Further features of the invention pertain more particularly to the specific arrangement of the substation apparatus and of the automatic switching apparatus embodied in the system,

whereby the above-outlined and additional operating features are obtained.

The novel features believed to be charateristic of the invention are set forth with particularity in the appended claims. The invention, both as to its organization and method of operation, together with further objects and advantages thereof, will best be understood by reference to the specification taken in connection with the accompanying drawing in which the single figure illustrates an automatic telephone system having embodied therein the features of the invention briefly outlined above.

Referring now to the drawing, the system there illustrated comprises a plurality of lines, three of which are indicated at lo, M and i2, extending respectively to the substations A, B and C, together with automatic switching apparatus for setting up connections between the lines. More particularly, the automatic switching apparatus comprises line switches l3, l4 and I5 individually terminating the lines H], H and E2 in the order named; and a plurality of first selector switches one of which is indicated at It, each having access to a. group of second selector switches one of which is indicated at ii, and to a plurality of special connector switches one of which is indicated at IS. The automatic switching apparatus further comprises a plurality of regular connector switches one of which is indicated at It, these switches being arranged in groups and each having access to a plurality of the subscribers lines of the system. Each of the first selector, second selector and connector switches such, for example, as the switches [5, ll, i8 and I9 includes a trunk line incoming thereto over which the switch may be seized from any one of a group of preceding switches. These trunk lines individually comprise a pair of talking conductors and a private or control conductor. Preferably, the line switches l3, l4 and I5 and the other similar switches individually terminating the subscribers lines of the system are of the well-known non-homing rotary type while the first selector, second selector and connector switches are of the well-known Strowger type of which several commercial embodiments are available. Each of the connector switches of the system is of the wellknown calling party release type. In order more clearly to explain the operation of the system, a portion of the control equipment embodied in each of the switches l6, 11, I8 and I9 is illustrated in detail. More particularly, the relay equipment embodied in the first selector switch 16 includes a line relay I00 and a switching-through relay H0 which latter relay functions in response to operation of the swich IE to select an idle outgoing trunk line to switch the calling loop circuit through to the succeeding switch to which the idle trunk line extends. The control apparatus of the second selector switch similarly comprises a line relay l20 and a switching-through relay I39. If desired, each of the first and second selector switches corresponding to and including the switches i6 and il may be of the arrangement described in the book entitled Telephone Theory and Practice; Automatic switching and auxiliary equipment, page 69, written by Kempster B. Miller and published by the MoGraw-Hill Book Company in 1933. The special connector switch I8 is of the capacitance bridge type and may be of the general arrangement disclosed on page '75 of the above-mentioned publication. The control apparatus of this switch comprises a line relay I43 and a slow-acting ring cut-off and line switching relay I56. A pair of condensers MI and I42 are serially incorporated in the conductors of the trunk line incoming to the switch I8 for the purpose of separating the calling and called loop circuits extending to this switch when a connection routed by Way thereof is fully established. The regular connector switch [9 may be of the same general arrangement as the connector switch 18 and has embodied therein a line relay Ill] and 9. called party answer or battery reversing relay 180.

The switching apparatus describe above is illustrated as comprising a part of the apparatus embodied in a single automatic exchange. In the event this exchange forms a part of a larger exchange network and facilities are to be provided whereby the various subscribers of the network may call through two or more exchanges without the assistance of an operator, the first selector switches such, for example, as the switch It may be given access to one or more groups of outgoing repeaters terminating trunk lines extending to the other exchanges. In such case, the exchange battery voltage normally impressed across the talking conductors of the trunks extending from the bank contacts of the first selector switches to the outgoing repeaters may be poled to correspond to the polarity of the voltage normally impressed across the talking conductors of the trunk lines incoming to the regular connector switches, all in the manner more fully explained subsequently, for the purpose of preventing the substations equipped for restricted service from routing calls by way of these repeaters to substations outside of the restricted area.

Referring now more particularly to the substation A, the apparatus provided at this substation comprises a transmitter 20, a receiver 2!, a dial operated calling or impulsing device 22 and a hook or cradle switch 23 which is operative from its normal position as shown in the drawing, to its oil-normal position to complete a loop circuit including the conductors of the line If! and extending to the line switch l3. For the purpose of blocking the flow of current of one polarity over the line i ii, there is provided a unidirectional conductive device in the form of a copper oxide rectifier 24 which is adapted to be included in the loop circuit established by way of the line It when the hook switch 23 is operated to its oilnormal position. This device is shunted by capacitance means in the form of a condenser 25, thereby to provide a signal current by-pass when the device is operatively included in an established loop circuit including the line H]. The apparatus provided at the substation A further comprises coin receiving means which includes a coin deposit channel or chute 26, a coin collect channel or chute 21 and a coin refund channel or chute 28. For the purpose of short-circuiting the rectifier 24 when a coin is deposited in the coin deposit chute 26 of the coin receiving means, there by to condition the substation circuit for unlimited service, there is provided a switching device 29 comprising two movable contact springs 29a and 29b and an actuating member 30 which projects within the coin deposit chute 26. The free ends of the movable contact springs 29a and 2% respectively cooperate with latching elements 3 la and 3lb, both mounted near the free end of a cantilever mounted spring 32. The movable contact spring 290. in cooperation with its associated fixed contact is arranged to complete a low impedance path comprising a resistor 33 for shunting the transmitter 20. This path, when completed, renders the transmitter ineffective to transmit signal currents over the line H), although permitting a suihcient portion of incoming signal currents to traverse the receiver 2| to cause audible reproduction thereof. In order to interrupt this path following the completion of a desired taiking connection, there is provided a key operated switching device 34 which includes four contact springs 34a, 34?), Ste and Sid, and an actuating member 35 which is arranged to cooperate with the latching spring 33 to move the two latching elements em and 35b out of engagement with the springs Eta and 2%, respectively. The actuating member 35 is also arranged to operate a rocker arm 36 which normally projects within the coin collect chute 21 to prevent a coin deposited in the coin deposit chute 26 from passing into the coin collect chute 2?. The key operated switching device 34 is of the locking type. More particular-.51, the device includes a latching element 3? which is normally biased into engagement with the free end of the contact spring 352a by means of a cantilever mounted biasing spring 33. This latching element is arranged to be operated out of engagement with the spring 3 3a by means of an operating magnet 39 which, when energized, attracts a magnetic armature member, not shown, carried by the spring 38. For the purpose of preventing coins deposited in the coin deposit channel 26 of the coin receiving means from passing into the coin refund chute 28, there is provided a rocker arm 46 which is arranged to be controlled by a second key operated switching device including an actuating member i! spring re. The actuating member A! is also arranged to operate the spring 32in order to move the latching elements em and 3th out of engagement with the springs 29a and 2%, respectively. The movable contact spring d2 of the second switching device is provided for the purpose of interrupting an established loop circuit extending by way of the line i9, thereby to initiate the release of an operated switch train,

in any case when this device is operated to obtain the refund of a deposited coin. In order to insure the release of the operated switch train each time a coin refund operation is performed, there is operatively associated with the actuating member ll a slow-acting device in the form of a dashpot 43 which functions to retard movement of the member M from its cit -normal position to its normal position.

Referring now more particularly to the operation of the system and considering first calls originating at the substation A, it is pointed out that such calls are initiated in the unusal manner by removing the receiver 2! from the supporting hook of the hook switch 23. When this operation is performed the hook switch 23 is operated to its off-norma1 position to open, at its springs 23a and 23b, a point in the circuit traced hereinafter for energizing the release magnet 39, and to complete a loop circuit extending to the line switch i3. This loop circuit may partially be traced as extending by way of the line conductor illa, the pulsing springs 22a of the impulsing device 22, the rectifier 24, the switch spring 230 and the associated switch hook, the transmitter 25, the receiver 2i and the contact spring 132 to the opposite line conductor we. The line switch i3 responds to completion of this loop circuit by operating in the usual manner to mark the calling line 26 as busy in bank contacts of the connector switches having access thereto and t select and a movable contact an idle one of the first selector switches to which it has access. Assuming, for example, that the first selector switch It is the first idle one of the selector switches to which the line switch it has access, when the trunk line extending to this selector switch is tested and found to be idle, the line switch I3 operates to switch the calling loop circuit through thereto, thereby to energize the line relay me. In this regard, it is pointed out that the exchange battery is connected to the windings of the line relay embodied in the line switch is and of the line relay H30 in a manner such that current flow over the established loop circuit is not blocked by the rectifier 24 included therein. Foliowing the completion of this loop circuit and when the line relay mil operates, the remaining control apparatus of the selector switch It is conditioned to respond to the first operation of the impulsing device 22 provided at the substation A.

The next operation performed by the calling party using the substation A depends upon the type of call being initiated. Thus, if the call is to be forwarded to the telephone station B, for example, which may be reached without a coin deposit, the calling party proceeds to dial the directory number of this substation in the usual manner. Alternatively, if the call is to be forwarded to a substation such, for example, as the substation C associated with a line terminating at one of the regular connector switches of the system, the calling party must first deposit a coin in the coin deposit chute 26 before more than one digit is dialed and preferably before the dialing operation is started. Assuming first that the call under consideration is to be forwarded. to the telephone substation B, the impulsing device 22 is operated in accordance with the directory number designating the called substation. During each operation of the calling device the pulsing springs 22a, are opened and closed one or more times depending upon the character of the digit dialed. The line relay I68 of the first selector switch l6 follows the impulses of the first digit and repeats these impulses to the vertical magnet of the switch 16 in the usual manner, whereby the wipers of the switch are elevated to a position opposite the level of bank contacts terminating the desired group of trunk lines. At the end of the digit and during the inter-digit pause between the first and second operations of the impulsing device 22, the rotary magnet conventionally embodied in the switch 16 functions to rotate the wipers of this switch over the bank contacts terminating the selected group of trunk lines until an idle one of these lines is selected. If, for example, the connector switch I8 is one of the group of connector switches selected in response to the group selecting operation of the selector switch it and further the switch I8 is the first available idle switch of the selected group, when the wipers of the selector switch it engage the contacts terminating the conductors of the trunk line extending to this connector switch, the switching-through relay 5 ii! is energized and operates in the usual manner. Upon operating, the relay I It, at its armatures I i l and l I 2 and their respective associated working contacts, switches the calling loop circuit through to the selected connector switch is causing the line relay I49 embodied in this connector switch to be energized. The line relay Hi9 now operates, it being pointed out that the exchange battery is connected to the battery terminals of this line relay i-na manner such that the recti fier 24 does not block the flow of current over the loop circuit. Upon operating, the relay I40 causes the operation of the hold relay, not shown, but conventionally provided in the connector switch I8. The hold relay, in turn, operates to impress ground potential upon the private conductor of the trunk line incoming to the connector switch I8, thereby to maintain the switchingthrough relay I II] of the preceding selector switch I6 operated and to guard this connector switch against seizure by another of the first selector switch having access thereto. Following the operations just described, the connector switch I8 is conditioned to respond to the impulses transmitted over the calling loop circuit incident to further operation of the impulsing device 22. The line relay I40 follows the impulses of the second digit and functions to repeat the impulses to the vertical magnet embodied in the connector switch I8. As a result, the wipers of this switch are elevated, in the usual manner, to a position opposite the level of bank contacts terminating the group of lines including the line II. Thereafter and when the third digit is dialed at the calling substation, impulses are delivered, through operation of the line relay I40, to the rotary magnet of the connector switch I8 so that the wipers of this switch are rotated into engagement with the set of contacts terminating the conductors of the line II. At the end of the third digit the selected line is tested in the usual manner to determine the idle or busy condition thereof and, if busy, busy tone current is returned over the calling loop circuit to signal the calling party that the desired connection cannot be obtained. Alternatively, if the line II is idle at the time it is selected, the control apparatus embodied in the connector switch I8 automatically operates to project ringing current over the line for the purpose of energizing the signal device provided at the substation B, and to return the usual ring-back tone signal to the calling party. When the call is answered at the called substation, a direct current bridge is connected across the conductors of the line II to complete a circuit including the armatures I! and I52 of the ring cut-off relay I50 for energizing the upper winding of this relay. Upon operating, the ring cutoff relay I50 completes, at its armature I53, a locking circuit for itself and thereafter completes, at its armatures I5I and I52 and their respective associated working contacts, the desired communication connection between the calling and called substation.

The release of the connection established in the manner just described is entirely under the control of the calling party. More particularly, when the receiver 2| is replaced upon its supporting hook to cause operation of the hook switch 23 from its oif-normal position to its normal position, the switch hook is disengaged from its asssociated contact 23c to interrupt the loop circuit extending from the substation A to the operated connector switch I8. As a result, the line relay I40 is deenergizod and restores to initiate the release of the connector switch I8 in the usual manner. During the release of this connector switch, ground potential is removed from the control or private conductor of the trunk line extending thereto, whereby the preceding operated.- selector switch it is released in the usual manner. When ground potential is removed from the private conductor of the trunk line extending to the selector switch IS, the line switch I3 is also restored to normal in a conventional manner. During the release of this line switch, ground potential is removed from the privatae conductor of the calling line IEI so that this line is marked as idle in the bank contacts of the connector switches having access thereto. Thus, the apparatus utilized in establishing the connection is fully released and is rendered available for further use.

From the preceding explanation with reference to the call routed to the substation B, it will be apparent that the calls may be successfully completed so long as the unidirectional conductive device 24 does not interfere with the flow of direct current over an established calling loop circuit extending from the substation A, as this loop circuit is successively extended to the selector and connector switches. In the call just described, the failure of the device 24 to block the flow of direct current over the calling loop circuit is due to the manner in which the line relays I and I40 respectively embodied in the switches I6 and I3 are connected to the exchange battery. It will be apparent, therefore, that calls originating at the substation A and routed through the special switches corresponding to and including the con nector switch I8 to specified ones of the substation lines embodied in the system may be successfully completed without coin deposits at the calling substation. On the other hand, if a calling party at the substation A attempts to obtain a connection to a substation associated with a line not accessible to the special connector switches, the undirectional conductive device 24 functions to block the progress of the call after it proceeds to a certain point. Thus, if a calling party attempts, without making a coin deposit, to route a connection to the substation line I2 by dialing the directory number of the substation C, the first two digits dialed cause the connection to be routed to one of the regular connector switches of the system. Assuming that the switches I6 and I! are successsfully operated in response to the first two digits dialed at the substation A and further that the second selector switch I! operates to seize the connector switch I9 having access to the called line I2, when the calling loop circuit is switched through to this connector switch the voltage oil the exchange battery is impressed upon this loop circuit through the windings of the line relay I'iIl. This line relay is reversely connected to the exchange battery. Hence, the polarity of the voltage impressed upon the calling loop circuit is such that the unidirectional conductive device 24 blocks the flow of current over this circuit, and the line relay Ill! does not operate. Accordingly, the hold relay conventionally embodied in the connector switch I9 and controlled by the line relay I'Ii] does not operate and holding ground potential is not impressed upon the control conductor of the trunk line incoming to the connector switch I9. The absence of ground potential from the indicated control conductor causes the preceding selector switches I1 and IE to be released. Since the calling loop circuit including the calling line I0 is not interrupted during the release of the two switches I6 and H, the first-mentioned of these switches is reseized immediately following its release. Hence, the last two digits of the directory number designating the substation C and dialed at the calling substation are absorbed by the selector switch I6 and an idle second selector switch or connector switch seized by the switch I6. Thus, the call intended for the substation C is not completed. The calling subscriber, upon failing to receive the usual ring back tone signal, will, of

course, replace the receiver 2! upon the switch hook of the hook switch 23, thereby to interrupt the calling loop circuit and to initiate the release of the operated switch train in the previously described manner.

As previously indicated, if the dialing operation is preceded by the deposit of a coin in the coin receiving means, the rectifier 24 is rendered ineffective to restrict the effective operation of the impulsing device 22. Thus, in making the call just considered, if the calling party deposits a coin in the coin deposit chute 26 following removal of the receiver 2| from the switch hook and prior to operation of the calling device 22, the passage of this coin through the coin deposit channel 26 causes the switch 29 to operate and short-circuit the rectifier 24. More particularly, when the deposited coin engages the actuating member 35 the movable contact springs 29a and 2% are moved to the left into engagement with their respective associated fixed contacts and the free ends of these springs are moved over the latching elements em and 3th, respectively, permitting the spring 32 to flex upwardly so that the indicated latching elements restrain the springs 29a and 29b in their respective operated positions. With the contact spring 2% engaging its asssociated fixed contact, an obvious path is completed for short-circuiting the rectifier 24 and with the contact spring 29a engaging its associated fixed contact, the above-mentioned low impedance path including the resistor 33 is completed for short-circuiting the transmitter 22; in series with the receiver 2!. With the rectifier 2G excluded from the calling loo-p circuit, it will be apparent that the direction of current flow over this circuit may be reversed at will as the call proceeds through the automatic switching apparatus of the line terminating exchange. Accordingly, in the case under consideration the call may be routed through the switches it, I! and IS in succession to the desired called line l2. When the call is answered at the called substation C, a d rect current bridge is connected across the conductors of the line 12 and the battery reversing relay lot? is caused to operate in the usual manner. This relay, upon operating, actuatesits armatures I8| to I84, inclusive, to reverse the direction of current flow over the loop circuit extending through the switches 15 and H to the calling substation. Following the completion of the desired talking connection in the manner just described, the receiver 2| responds to signal currents transmitted over this connection to the substation A to a sufhcient extent to enable the calling party to determine that the call has been answered, even though the low impedance shunt path comprising the resistor 33 prevents the major portion of the signal currents from traversing the windings of the receiver. The transmitter 25, on the other hand, is rendered substantially inoperative to transmit signal currents over the line I!) so long as this low impedance path is completed. In order to render the transmitter 26 operative, the calling party, upon ascertaining that the call has been answered, depresses the actuating member 35 of the switch 34, thereby to cause the low impedance path shunting the transmitter 2% and the receiver 2! to be interrupted. More particularly, when the member 35 is) depressed the switch springs S lb, 3G0 and 3M are first operated into engagement to complete obvious paths for short-circuiting the rectifier 24 and the pulsing spring 2211 of the impulsing device 22. During such movement of the member 35 the spring 34a is also operated into engagement with its associated fixed contact to prepare the previously mentioned circuit for energizing the release magnet 39. During the downward movement of the spring 34a the free end of this spring rides over the latching element 3'! permitting the spring 38 to flex to the left, thereby to latch the spring 34a and the member 35 in their respective operated positions. During the downward movement of the member 35 the free end of the cantilever mounted spring 32 is moved downward so that the latching elements 35a and M22 are carried out of engagement with the free ends of the contact springs 29a and 29b. Accordingly, these springs are permitted to return to their respective normal positions out of'engagement with their respective associated fixed contacts. Thus, the first completed path for short-circuiting the rectifier 24 is interrupted and the above-traced low impedance path shunting the transmitter 20 is opened, thereby to render this transmitter operative to project signal currents over the established talking circuit. As the member 35 of the switch 34 is depressed in the manner just explained, it functions to rock the arm 36 in a clockwise direction so that the coin blocking finger of this arm is moved out of the coin collect chute 21, permitting the coin deposited in the chute 26 to pass from this chute into the coin collect chute 2! and through this chute into the usual coin collect box. It will be noted that in any case when the member 35 is operated to complete the path short circuiting the rectifier 24, the springs 34b, 34c and 34d. are moved into engagement to short circuit the pulsing springs 22a. Thus, the switch 34 cannot be operated to short circuit the rectifier without endering the impulsing device ineffective to transmit control pulses over the line It and fraudulent use of the apparatus is prevented.

At the end of the conversation and when the connection is cleared out at the calling substation A, the operated switching apparatus comprising the switches l3, It, I? and i9 is released in the conventional manner briefly explained above. During the release of the apparatus the switch 34 is restored to normal when the receiver 2! is replaced upon the switch hook of the hook switch 23. More particularly, when the hook switch 23 is actuated from its off-normal position to its normal position, the spring 23a is first moved into engagement with the spring 2311 and thereafter the switch hook is moved out of engagement with the spring 23c, thereby to include the winding of the release magnet 29 in the calling loop circuit. Specifically, this magnet is energized over a circuit which may be partially traced as extending by way of the line conductor Hid, the switch springs 34d, 340, 3%, 23b and 2311., the winding of the magnet 39, the spring 34a and its associated fixed contact, the transmitter 2t, the receiver 2|, the contact spring 42 and the opposite line conductor iiib. When energized over this circuit the magnet 39 attracts the armature carried by the latching spring 38, causing this spring to be moved to the right so that the latching element 31 carried thereby releases the free end of the spring 340,. As a result, the key switch 34 is permitted to restore to its normal position. During such restoration of the switch 34, the spring 34a is moved out of engagement with its associated fixed contact to interrupt the calling loop circuit and thereby deenergize the winding of the magnet 39. Also during restoration of the switch 34, the spring 32 and the rocker arm 3% are restored to their respective normal positions and the springs 34b,

340 and 34d are moved out of engagement to open the above-described paths for, short-circuiting the pulsing springs 22a and the rectifier E i. Thus, the apparatus provided at the substation A is fully restored to normal.

If a call initiated at the substation A is not successfully completed due to the busy condition of the called line or is abandoned before the dialing operation is completed, the operated switch train through which the call is routed is released in the usual manner when the receiver 2| is replaced upon the switch hook of the hook switch 23. In such case, if a coin has been deposited in the coin deposit chute 26 of the coin receiving means, it is held between the coin blocking fingers of the two rocker arms 36 and and the switch 23 is restrained to its off-normal position. In order to restore the switch 29 to normal and to obtain a refund of the deposited coin, the callins party may depress the key or member 4!. When this key is moved downward the spring 32 is moved to disengage the latching elements (Ma and 3H; from the springs 29a and 291) so that the switch 29 is permitted to restore to normal. During the downward movement of the key il the rocker arm is also rotated in a counter-clockwise direction so that the coin blocking finger thereof is moved out of the coin refund chute 26, permitting the deposited coin to pass into the refund chute 23 and by way of this chute to the coin refund pocket conventionally embodied in substations of the paystation type. Operation of the key 4-! further results in movement of the contact spring 42 out of engagement with its associated fixed contact to open a. point 4 in the previously traced loop circuit including the conductors of the line in and extending to the line switch it. The purpose of providing the switching elements comprising the contact spring 42, in association with the key 4|, is to prevent fraudulent use of the substation apparatus. More particularly, these switching elements insure the interruption of an established calling loop circuit in any case when a coin refund is obtained. This interruption of the calling loop circuit in turn results in the release of the operated switch train in the usual manner. It will be apparent, however, that, if the switching elements controlled by the key M were operated out of engagement and then back into engagement with sufficient rapidity, it might be possible for a user of the apparatus to obtain a coin refund without releasing an established switch train. In order to obviate this possibility, the member li is mechanically connected to the plunger of the dashpot 43, this dashpot being so arranged that movement of the member l! back to its normal position following operation thereof to disengage the spring 42 from its associated fixed contact is retarded a sufficient amount to permit the complete release of an operated switch train before the spring 42 reengages its associated fixed contact. The provision of the dashpot 43, operatively associated with the member M, also prevents this member from being intermittently operated to transmit switch control pulses over the line l6 for the purpose of securing an unauthorized connection without a coin deposit.

On a call incoming to the substation A, the signal device 9 is energized to indicate the presence of the incoming call on the line It) when ringing current is projected over this line from the operated connector switch through which the call is routed. With the arrangement illustrated,

the party who answers the call may, by first removing the receiver Zl from the switch hook of the hook switch 23 and then depressing the actuating member 35 of the switch 34, cause the desired conversational circuit to be completed in the usual manner, regardless of the arrangement of the connector switch through which the call is routed. Thus, with the switch 34 operated to its off-normal position, the rectifier 24 is shunted from the line so that current of either polarity may flow over this line. Accordingly, the battery cut-off relay embodied in the connector switch through which the call is routed is caused to operate, regardless of the manner in which the windings of this relay are connected to the exchange battery. In order more fully to explain this feature of the system, it may be assumed, for example, that a call is forwarded through the connector switch iii to the substation A. When the call is answered at the substation A and the above-described operations are performed incident to the answering of the call, a direct current bridge excluding the rectifier 24 is established across the conductors Illa and H32) of the line it so that the ring cutoif relay I50 is energized and operated to cause the desired conversational circuit to be completed. It will be noted that with the windings of this relay connected to the exchange battery in the manner illustrated, operation of the switch 3'? is unnecessary. More specifically, the direction of current flow over the established loop circuit is from the positive terminal of the exchange battery by way of the armature i522, the line conductor l lb over the bridging path between this conductor and the opposite conductor lfic, the conductor ma, the armature ifii and the upper winding of the relay to the negative terminal of the exchange battery. Since the rectifier 24 is poled to permit current to pass over the line I5 in this direction, operation of the ring cut off relay I50 is effected even though the switch 3 5 is not operated. If, however, the call to the substation A is routed through a connector switch having a ring cut-off relay connected to the exchange battery over connections which are the reverse of those shown, for the ring cut-off relay I59, the direction of current flow is from the line conductor loa to the line conductor lilb. In such case, the rectifier 24 functions to block the flow of current, thereby to prevent operation of the ring cut-off relay embodied in the connector switch through which the call is routed. Accordingly, the desired talking circuit cannot be established without operation of the switch 34. From the foregoing explanation it will be apparent that, by incorporating rectifiers in the lines extending to substations other than paystations, the switching apparatus serving the lines may be so arranged that calls incoming to such lines can only be successfully completed if they are routed through connector switches which include ring cut-off relays having windings connected to the exchange battery in a predetermined manner.

Although the invention has been described primarily with reference to its use in a substation of the paystation type, it will be understood that the rectifier 24 may be utilized, without changing the circuit connections disclosed, as ameans of restricting the service available to a regular substation in which it is included. Thus, by a suitable arrangement of the switching apparatus used in substations incorporating rectifier elements arranged in the manner shown, the substations may be limited to calls to other substations located within a predetermined area. Furthermore, the switching apparatus may be so arranged that interexchange calls are prevented although all other calls are permitted. In the latter case, the repeaters associated with the interofiice trunk lines may include line relays having windings connected to the exchange battery in a manner such that when one of the repeaters is seized, the rectifier embodied in the calling subscribers substation apparatus functions to block the flow of direct current over the calling line, thereby to initiate the release of the established switch train through which the call is routed. In view of the foregoing description it is .believed that themanner in which such repeaters could be arranged is fully apparent without further explanation.

While there has been described what is at present considered to be the preferred embodiment of the invention, it will be understood that various modifications may be made therein and it is intended to cover in the appended claims all such modifications as fall within the true spirit and scope of the invention.

What is claimed is':

1. In a telephone system, a substation including a transmitter, a receiver and means for receiving a coin or the like, a line extending to said substation, a normally incomplete low impedance path for shunting said transmitter and efiective, when completed, to render said transmitter ineffective to transmit signal currents over said line, means comprising a unidirectional conductive device for preventing the flow of direct current of one polarity over said line, switching means operative in response to the deposit of a coin in said coin receiving means for rendering said device ineffective to prevent the flow of direct current of said one polarity over said line and for completing said path, additional switching means also operative to render said device ineffective to prevent the flow of direct current of said one polarity over said line, and means responsive to operation of said additional switching means for interrupting said path.

2. In a telephone system, a substation including means for receiving coins or the like, said coin receiving means including a coin deposit channel and a coin collect channel, a line extending to said substation, means comprising a undirectional conductive device for preventing the flow of direct current of one polarityover said line, switching means operative in response to the deposit of a coin in said coin deposit channel for rendering said device inefiective to prevent the flow of direct current of said one polarity over said line, additional switching means also operative to render said device ineffective to prevent the flow of direct current of said one polarity over said line, and means responsive to operation of said additional switching means for permitting a coin deposited in said coin deposit channel to pass into said coin collect channel.

3. In a telephone system, a substation including a transmitter, a receiver and means for receiving coins or the like, said coin receiving means including a coin deposit channel and a coin collect channel, a line extending to said substation, a normally incomplete low impedance path for shunting said transmitter and efiective, when completed, to render said transmitter ineffective to transmit signal currents over said line, means comprising a unidirectional conductive device for preventing the flow of direct current of one polarity over said line, switching means operative in response to the deposit of a coin in said coin deposit channel for rendering said device ineffective to prevent the flow of'direct current of said one polarity over said line and for completing said path, additional switching means also operative to render said device ineffective to prevent the flow of direct current of said one polarity over said line, means responsive to operation of said additional switching means for interrupting said path, and means also responsive to operation of said switching means for permitting a coin deposited in said coin deposit channel to pass into said coin collect channel.

4. In a telephone system, a substation including a transmitter, a receiver, means for receiving coins or the like and a hook or cradle switch operative between a normal position and an off -normal position, a line extending to said substation, means comprising a unidirectional conductive device for preventing the flow of direct current of one polarity over said line, switching means operative in response to the deposit of a coin in said coin receiving means for rendering said device ineffective to prevent the flow of direct current of said one polarity over said line, additional switching means having a normal position and operative to an off-normal position also to render said device ineffective to prevent the flow of direct current of said one polarity over said line, and means responsive to operation of said hook switch from its ofi-normal position to its normal position for causing said additional switching means to be restored to its normal position.

5. In a telephone system, a substation including a transmitter, a receiver, means for receiving coins or the like'and a hook or cradle switch operative between a normal position and an of)?- normal position, a line extending to said substation, a normally incomplete low impedance path for shunting said transmitter and effective, when completed, to render said transmitter ineffective-to transmit signal currents over said line, means comprising a unidirectional conductive device for preventing the flow of direct current of one polarity over said line, switching means operative in response to the deposit of a coin in said coin receiving means for rendering said device ineffective to prevent the flow of direct current of said one polarity over said line and for completing said path, additional switching means having a normal position and opera tive to an ofi-normal position also to render said device ineffective to prevent the flow of direct current of said one polarity over said line, means responsive to operation of said additional switching means to its ofi-normal position for interrupting said path, and means responsive to operation of said hook switch from its oiT-normal position to its normal position for causing said additional switching means to be restored to its normal position. I

6. In a telephone system, a substation including means for receiving coins or the like, a line extending to said substation, means comprising a unidirectional conductive device for preventing the flow of direct current of one polarity over said line, a switching device having a normal position and operative to an off-normal position in response to the deposit of a coin in said coin receiving means, means controlled by said switching device for rendering said unidirectional conductive device ineffective to prevent the flow of direct current of said one polarity over said line, additional switching means and means controlled thereby for also rendering said unidirectional conductive device inefiective to prevent the flow of direct current of said one polarity over said line, and means responsive to operation of said additional switching means for causing said switching device to be restored to its normal position.

7. In a telephone system, a substation including a transmitter, a receiver, means for receiving coins or the like and a hook or cradle switch operative between a normal position and an offnormal position, a line extending to said substation, a normally incomplete low impedance path for shunting said transmitter and effective, when completed, to render said transmitter ineffective to transmit signal currents over said line, means comprising a unidirectional conductive device for preventing the flow of direct current of one polarity over said line, a switching device having a normal position and operative in response to the deposit of a coin in said coin receiv ing means to short-circuit said unidirectional conductive device and to complete said path, additional switching means having a normal position and operative to an off-normal position to short-circuit said unidirectional conductive device, said switching device being operative to its normal position to interrupt said path in response to operation of said additional switching means to its ofi-normal position, and means responsive to operation of said hook switch from its off-- normal position to its normal position for causing said additional switching means to be restored to normal.

8. In a telephone system, a substation including means for receiving coins or the like, a line extending to said substation, means comprising a unidirectional conductive device for preventing the flow of direct current of one polarity over said line, a switching device having a normal position and operative to an off-normal position in response to the deposit of a coin in said coin receiving means, means controlled by said switching device for rendering said unidirectional conductive device ineffective to prevent the flow of direct current of said one polarity over said line, additional switching means and means controlled thereby for also rendering said unidirectional conductive device inefiective to prevent the flow of direct current of said one polarty over said line, means responsive to operation of said additional switching means for causing said switching device to be restored to its normal position, and a second switching device operative to interrupt a loop circuit established by way of said line, said first-named switching device being operative from its off-normal position to its normal position in response to operation of said second switching device.

9. In a telephone system, a substation including a transmitter, a receiver, means for receiving coins or the like and a hook or cradle switch operative between a normal position and an offnormal position, a line extending to said substation, a normally incomplete low impedance path for shunting said transmitter and effective, when completed, to render said transmitter ineffcctive to transmit signal currents over said line, means comprising a unidirectional conductive device for preventing the flow of direct current of one polarity over said line, a switching device having a normal position and operative in response to the deposit of a coin in said coin receiving means to short-circuit said unidirectional conductive device and to complete said path, additional switching means having a normal position and opera-tive to an cit-normal position to short-circuit said unidirectional conductive device, said switching device being operative to its normal position to interrupt said path in response to operation of said additional switching means to its chi-normal position, means responsive to operation of said hook switch from its ofi-normal position to its normal position for causing said additional switching means to be restored to normal, and a second switching device operative to interrupt a loop circuit established by way of said line, said first-named switching device being operative from its off-normal position to its normal position in response to operation of said second switching device.

10. In a telephone system, a substation including a hook or cradle switch and means {or receiving coins or the like, said coin receiving means including a coin deposit channel and a coin refund channel, a line extending to said substation, means including said hook switch for establishing a loop circuit including said line, additional switching means having a first position and operative to a second position to interrupt said loop circuit, means controlled by said additional switching means for permitting a coin deposited in said coin deposit channel to pass into said refund channel, and a slow-acting device for retarding movement of said switching means from said second position to said first position.

11. In a telephone system, a substation including a transmitter, a receiver and means for receiving a coin or the like, a line extending to-said substation, a normally incomplete low impedance path for shunting said transmitter and effective, when completed, to render said transmitter in effective to transmit signal currents over said line, means comprising a unidirectional conductive device serially included in said line for preventing the flow of direct current over said line, capacitance means shunting said device to provide a bypass for signal currents, switching means operative in response to the deposit of a coin in said coin receiving means to short-circuit said device and complete said path, additional switching means also operative to short-circuit said device, and means responsive to operation of said additio nal switching means for interrupting said path.

12. In a telephone system, a substation including a hook or cradle switch and means for receiving coins or the like, said coin receiving means including a coin deposit channel and a coin refund channel, a line extending to said substation, a plurality of impulse responsive call forwarding switches controllable over a loop circuit including said line and successively operative in response to successive operations of said impulsing device, means including said hook switch for completing said loop circuit, circuit means for preventing said switches from responding to more than a predetermined number of operations of said device, means responsive to the deposit of a coin in said coin deposit channel for rendering said circuit means inefiective to restrict the effective operation of said impulsing device, additional switching means having a first position and operative to a second position to interrupt said loop circuit, means controlled by said additional switching means for permitting a coin deposited in said deposit channel to pass into said coin refund channel, means also controlled by said additional switching means for conditioning said circuit means to restrict effective operation of said impulsing device, and a slow-acting device for retarding movement of said additional switching means from said second position to said first position.

13. In a telephone system, a substation, a plurality of lines including one line extending to said substation, a plurality of automatic switches controllable over said lines to establish connections between said lines, a unidirectional conductive device adapted to be included in a calling circuit established by way of said one line, and means including said unidirectional conductive device for preventing calls originating at said substation from being routed through certain of said switches.

14. In a telephone system, a plurality of lines, a plurality of automatic impulse-responsive switches controllable over said lines to establish connections between said lines, a substation including an impulsing device operative to transmit impulses over one of said lines, a unidirectional conductive device adapted to be included in a calling circuit established by way of said one line, and means including said unidirectional conductive device for preventing more than a predetermined number of impulse digits, resulting from operation of said impulsing device, from efiecting operation of said switches to establish a connection.

15. In a telephone system, a substation, a plurality of lines including one line extending to said substation, a plurality of automatic switches controllable over calling circuits including said lines to establish connection between said lines, each of a first group of said switches being so connected and arranged that, when seized, current of one polarity is returned over the calling circuit extending thereto, each of a second group of said switches being so connected and arranged that, when seized, current of the opposite polarity is returned over the calling circuit extending thereto, a unidirectional conductive device adapted to be included in a calling circuit established by way of said one line, and means including said unidirectional conductive device for preventing current of said one polarity from flowing over said one line, thereby to prevent connections from being routed from said substation through the switches of said first group.

16. In a telephone system, a substation, a plurality of lines including one line extending to said substation, a plurality of automatic switches controllable over loop circuits including said lines to establish connections between said lines, each of a first group orf said switches being so connected and arranged that, when seized, current of one polarity is returned over the calling loop circuit extending thereto, each of a second group of said switches being so connected and arranged that, when seized, current of the opposite polarity is returned over the calling loop circuit extending thereto, a unidirectional conductive device serially connected in said one line and adapted to be included in a loop circuit established by way of said one line, and means including said unidirectional conductive device for preventing current of said one polarity from flowing over said one line, thereby to cause the release of a switch train through which a connection is routed from said one line to any one of the switches of said first group.

17. In a telephone system, a substation including means for receiving coins or the like, a plurality of lines including one line extending to said substation, a plurality of automatic switches controllable over said lines to establish connections between said lines, a unidirectional conductive device adapted to be included in a calling circuit established by way of said one line, means including said device for preventing calls originating at said substation from being routed through certain of said switches, and means responsive to the deposit of a coin in said coin receiving means for rendering said device inefiective to prevent calls originating at said substation from being routed through said last-named switches.

18. In a telephone system, a plurality of lines, a plurality of automatic impulse-responsive switches controllable over said lines to establish connections between said lines, a substation including means for receiving coins or the like and an impulsing device operative to transmit impulses over one of said lines, a unidirectional conductive device adapted to be included in a calling circuit established by way of said one line, means including said unidirectional conductive device for preventing more than a predetermined number of impulse digits, resulting from operation of said impulsing device, from efiecting operation of said switches to establish a connection, and means responsive to the deposit of a coin in said coin receiving means for rendering said unidirectional conductive device ineffective to restrict the effective operation of said imp-ulsing device.

19. In a telephone system, a substation including means for receiving coins or the like, a plurality of lines including one line extending to said substation, a plurality of automatic switches controllable over loop circuits including said lines to establish connections between said lines, each of a first group of said switches being so connected and arranged that, when seized, current of one polarity is returned over the calling loop circuit extending thereto, each of a second group of said switches being so connected and arranged that, when seized, current of the opposite polarity is returned over the calling loop circuit extending thereto, a unidirectional conductive device adapted to be included in a loop circuit established by way of said one line, means including said unidirectional conductive device for preventing current of said one polarity from flowing over said one line, thereby to prevent connections from being routed from said substation through the switches of said first group, and means responsive to the deposit of a coin in said coin receiving means for rendering said device ineffective to prevent current of said one polarity from flowing over said one line.

20. In a telephone system, a substation, a line extending to said substation, a plurality of automatic switches having access to said line and operative to route connections to said line, and means comprising a unidirectional conductive device serially included in said line for preventing certain of said switches from operating to complete connections including said line.

21. In a telephone system, a substation, a line extending to said substation, a plurality of automatic switches having access to said line and operative to route connections to said line, means comprising a unidirectional conductive device serially included in said line for preventing certain of said switches from operating to complete connections including said line, and switching means at said substation for short-circuiting said device, thereby to render said last-named switches operative to complete connections including said line.

CLARENCE E. LOMAX.

Images