US2235910A - Telephone system - Google Patents

Description

March 25, 1941. P. v. WELCH TELEPHONE SYSTEM 2 Sheets-Sheet l Filed Dec.

WEA/rox? R l/. WELCH 2% @iw/#5W ATTORNEY March 25, 1941. P V, WELCH 2,235,910

TELEPHONE SYSTEM Filed Dec. 5, 1939 2 Sheets-Sheet 2 /NVENTOR 4 By R l/. WELCH WWW/M rmfom/Ey Patented Mar. 25, 1941 UNITED STATES PATENT OFFICE Telephone Laboratories,

Incorporated, New

York, N. Y., a corporation of New York Application December 5, 1939, Serial No. 307,597

8 Claims.

This invention relates to telephone systems.

The objects of the invention are to improve the equipment employed in telephone exchanges for obtaining and transmitting to subscribers who are frequently absent from their telephones information with respect to calls made during their absence; to enable the service operator in the exchange who obtains these messages during the absence of a called subscriber to initiate the operation of recording mechanism at theabsent subscribers substation and to transmit the mes sages over his line to the substation where they are recorded for his information when he returns; and to accomplish these purposes without the use of local power supply equipment or other expensive devices on the subscribers premises.

The foregoing objects of the invention are realized by means of a system in which a party who has subscribed forthis service is provided with a simple and relatively inexpensive telegraph printer at his substation which is wholly under the control of the service operator in the exchange. A calling party who has made an unsuccessful call to one of these special service lines and wishes to leave a message for the absent subscriber proceeds to operate his dial in `accordance with a special code to obtain a connection with the service operator in the telephone exchange. Having obtained the operator, the calling party explains that his call to the special service line was unsuccessful and gives her the message he wishes transmitted to the absent subscribers station. Thereafter the oper- -ator obtains connection with the special service line over automatic switches and transmits the message by telegraph signals.

A feature of the invention is a system of this character in which the operator first transmits a signal over the subscribers line to disconnect the normally effective telephone instrument at the substation and to connect the printer to the line; in which the power for operating the printer motor is then supplied from a source at the central office over the subscribers line to the substation; and in which the operating current iiowing over the subscribers line to drive the printer motor also serves to maintain the equipment at the substation in condition for receiving the telegraph signals which the operator now proceeds to transmit over the line to the printer. An advantage of this system is that the subscribers substation is normally in condition for the use of his telephone, no special operation being required on his part to convert the substation equipment tothe use of the printer instead of the telephone. An-

other distinct advantage is that the power for operating the printer is supplied from the central office, simplifying accordingly the equipment needed at the substation. p

In the drawings accompanying the detailed specication:

Figs. 1 and 2 illustrate a dial telephone system partly in diagrammatic form and partly in detail embodying the features of the invention.

Fig. 1 illustrates the subscribers lines, one of which is provided with a printer for recording messages, and the automatic switches used in establishing connections;

Fig. 2 discloses the circuits associ-ated with the service operators position and a telegraph transmitter for sending messages to the subscribers stations;

Fig. 3 shows a modified form of one of the substations equipped with a printer for recording the messages; and

Fig. 4 shows ya modified form of the switch calling lines', such as the line I, establish con` nections with other subscribers lines; the connector switch C--I, by which calling subscribers obtain connections with the service operator in the telephone exchange; and the connector switch C-2, by which the service operator obtains connections with subscribers lines entitled to the special service, may be of any suitable type, such as the switches commonly used in stepby step systems.

The subscribers line 2, which is entitled to the special service, is equipped at the substation with a small telegraph printer including a driving motor 3 and a printing magnet 4. The motor 3 is driven by alternating current supplied over the line 2 from the central ofiice, and the printing magnet is operated by direct current telegraph signals transmitted over the line from the operators position. The substation is also provided with a gas-filled discharge tube 5 which responds to a. seizure signal transmitted over the line from the operators position to prepare the substation for `an incoming telegraph message. The substation is further provided with a rectier 6 which converts the alternating current flowing in the line to direct current for operating a relay 1, which disconnects the subscribers telephone set and maintains the printer in operative relation to the line for the receipt of the incoming message.

The service operators position in the central office is equipped with a telephone transmitter 8 and receiver 9 for communication with subscribers who call her for the purpose of leaving messages for the absent subscribers. Also she has an impulse transmitter I5 for operating the automatic switches to extend connections from her position to the lines over which she wishes to transmit these messages. Furthermore, the operators position is equipped with a telegraph transmitter II for sending the messages over the connections which she has established to the subscribers lines and with a printer 99 for recording lthe massages sent.

The operators telegraph transmitter and the printers at the substations may be of any desired types, such, for example, as those disclosed in the patent to Zenner No. 2,173,147, of September 19, 1939, and in Zenner Patent No. 2,147,075 of February 14, i939.

The operation of the system will no'w be described, and to this end it will be assumed that the subscriber of line 2 is absent from his premises. During his absence the subscriber of ano-ther line, such as line I, may call him. The connection to the called line 2' is established in the usual manner over the line-finder switch F, selector switch S and connector switch C. Finding the called subscriber absent from his telephone and knowing that his line is entitled to special service, the calling subscriber releases the unsuccessful connection and dials a special code to operate the selector S and connector C-I to extend his line over the trunk circuit I2 to the service operators position. The connector C--I applies ringing current to the trunk I2, and this current iiows from one side of the trunk I2 through the condenser i3, thermistor It, lower winding of the relay I5, normal contacts of key I6 to the other side of the trunk I2. The thermistor I!! becomes heated andlowers its resistance, and sufficient current ows through the winding of relay I5 to attract the armature. Thereupon a circuit is closed from battery through the contacts of key II, upper winding and front contact of relay I5, signal lamp I8 to ground at the normal contacts of key I6.

The lighted lamp I8 attracts the attention of the operator, and she answers the call by moving the key I' to its intermediate position. The operation of key It to the intermediate position releases relay i5 and extinguishes the calling lamp I8 and also extends the trunk I2 to the operators position. The extended circuit may be traced from conductor I9 throughthe left closed contacts of key i6, conductor 29, right closed contacts of said key, conductor ZI, left contacts of key 22, right contacts. of key 22, conductor 23, condenser 5lA through the induction coil 2G, conductor 25, through the normal contacts and the impulse contacts 25 of the dial I0, conductor 2l, right 'norma-l contacts of key I6, left closed contacts of said key to conductor 2B. The operator converses with the calling subscriber, who informs her of the unsuccessful call and leaves with her any message that he may care to have transmitted to the calle-d party.

The operator, having made memoranda of the messages intended for the absent subscriber, proceeds to establish a connection between her position and his line. To do this she irst throws the key 22 to the intermediate position to establish a circuit from her impulse transmitter I9 over trunk 58 to the pulsing mechanism of the selector switch S-I and connector switch C- 2. The impulse circuit may be traced from the tip conductor 29, through the left closed contacts of key 22, coil 39, right closed contacts of said key, conductor 3I through the impulse contacts 2G of the transmitter Iii, conductor 2l, right normal contacts. of key 22, left closed contacts of said key to the ring conductor 32, extending to the selector switch S-I and connector switch C-2. The operator manipulates the dial I0 to transmit series `of impulses to the pulsing mechanism of the selector S-I and connector switch C-2. The selector and connector respond to these impulse series and step their brushes into engagement with the terminals of the subscribers line 2. During each impulse series the @1T-normal contacts of the dial I9 close a short circuit around the coil 36 to improve the pulsing operation.

After the connector C-Z has been set on the terminals of the called line, the operator moves the key 22 to its right-hand position. In this position a bridge is closed for holding the selector S-I and connector 0 2. This bridge may be traced from `conductor 29, left contacts of key 22, coil 39, right closed contacts of key 22, left contacts of the key to conductor 32. The key 22 also closes an operating circuit for relay 33, traceable from battery through the contacts of key Il, winding of said relay, conductor 311 to ground at the right contacts of key 22. Also the guard lamp i9 is lighted in an obvious circuit extending over conductor 34 to ground at the contacts of key 22. Relay 33 closes a circuit for sending a Seizure signal over the called line to operate the gas-lled tube 5 at the substation thereof.

This circuit may be traced from the positive pole of l20-volt battery 35, resistance lamp 59, normal contacts of relay 35, winding of relay 31 through the upper left winding of transformer 38, closed contacts of relay 33, conductor 39 thence through the tip brushes of the selector S-I and connector (1 -2, conductor 40, through the upper primary winding of transformer 4I, printer magnet 4, resistance 42, condenser 43, resistance Ml, winding of relay 55, closed contacts of key i5 to ground. Current flowing in.

this circuit charges the condenser 43 until it reaches the ionizing voltage of the control gap of the tube 5. When the ionizing voltage is reached, the tube res, and the anode circuit is established from the source at the central office over the circuit traced through the printer magnet l to the anode lil and cathode 4.8 of the tube, thence through the winding of relay 45 to ground at the key 46. circuit to operate the relay l5 at the substation but not the relay 3l at the central ofce. Relay e5 at its right contact extends the circuit, above traced, through the magnet fi, through rectier 6I and relay 35 to ground, thus excluding tube 5. Relay t5 also closes a parallel circuit from source 35, resistance lamp 59, normal contact of relay 35, relay 3'I, lower left winding of coil 38, thence over the ring side of the line, conductor 53, left contact of relay 55, lower left winding of transformer 5I, magnet t, right contact of relay 45, rectier 6I, winding of relay 45 to ground at key 46. Since these parallel circuits for magnet 4 short-circuit the tube 5, the latter becomes deionized. The increase of current due to these parallel paths and the inclusion of low resistance rectier 6I in place of the tube causes relay 3l to operate. Relay 3l at the central oice extinguishes the guard lamp 49 and operates relay 35 in a circuit from battery through the contacts of key I'I, winding of relay 35, front contacts of Suicient current hows in this` relay 37 to .ground over conductor 34. Relay 36 locks through its own front contact directly to the grounded conducto-r 34. The circuit for printer magnet 4 is `now transferred from l20 volt battery 35 to 80evolt battery 55 and may be traced from the latter through contacts of the operator-s telegraph sender magnet winding of printer 90, front contacts of relay 36, thence as traced over the line in simplex through magnet 4., relay 45, rectifier 6|, relay 45,v and' ground at key 46. By excluding the impedance of tube 5 suflicient current is derived from the reduced voltage at central office to insure the continued operation of relay at the lower voltage. The rectifier 6|, included in the circuit of relay 45, prevents the relay from locking on `central oi'lice talking or signaling battery.

Prior to the operation of relay 36 a. short circuit `exists across the conductors 33 and 5|) o-f the connection `extending to the called subscribers line. This short circuit may be traced from conductor 39 through the nor- Inal contacts of relay 36 and the operated contacts of relay 33 to conductor 56. Between the time, therefore, that relay 33 is operated and the operation of relay 36, no current `from the source 5| lio-ws over the called subscribers line. Instead of the short circuit for disabling source 5| during this interval a contact on relay 36 could be used, if desired, to hold open the primary winding of transformer` 38. As soon, however, as relay 36 yoperated as .above described, the short circuit is opened and alternating current from the source 5| flows in a loop circuit including the conductors of the called subscribiers line. This circuit may betraced from the upper left winding of the transformer 38, closed contacts of relay 33, conductor 33, tip brushes of `selector S-I and connector C2, conductor 4D thence in parallel through the driving motor 3 of the printer and the primary windings of trans former 4|, conductor 52, closed contacts of relay 45, conductor 53, ring brushes of connector C-Z and selectors- L conductor 50, closed contacts of relay 33 to the other terminal of the secondary winding of transformer 38. The motor 3 is driven in this circuit to supply the necessary .power for operating the printer. Also an alternating Voltage is induced inthe secondary winding of transformer 4 and the current resulting therefrom is rectified by the rectifier 6 and applied to the winding of relay Relay 'l operates and disconnects the telephone set 54 from the line. Relay 'l also closes a short circuit around the relay 45 and rectifier 6|, and relay 45 releases. Relay 'I now maintains the operating circuit for Y the printer magnet 4 and the circuit for supplying the alternating current to the transformer 4| and motor 3. The printer magnet operating circuit may be traced from the positive pole o-f battery 55 through the transmitting contacts of the operators telegraph transmitter Il, magnet winding of printer 90, closed contacts of relay 36, winding of relay 3l to the mid-point of the secondary winding of transformer 38, thence in a simplex circuit through the contacts of relay 33 over conductors 39 and 50 and conductors 40 and 53 of the subscribers line, the conductor 46 extending through the upper primary winding of transformer 4|, the conductor 53 extending through closed contacts of relay 1, conductor 52 and the lower primary winding of transformer 4|, the circuit 'continuing from the middle point of the vprimary winding through the printer magnet4, closedfcontacts of relay 'l to .ground at the contacts of key 46. The alternating current circuit is the same as previously described, except that it now extends through a front contact of relay 'l instead of relay 45.

The circuits are now in condition for the sending of telegraph messages to the called subscribers station. The operator proceeds to send whatever messages she may have for the absent subscriber by manipulating her telegraph transmitter |I to send telegraph signals over the simplex circuit through the printer magnet 4 at the called station. After the messages have been transmitted and recorded by the printer in the well-known manner, the operator releases the connection she has established to the subscribers line by restoring the key 22 to its normal or left-hand position. The restoral of the key removes ground potential from conductor 34 and relays 33, 36 and 3l release. Relay 33 opens the printing circuit and also opens the i circuit for supplying alternating current to the motor 3 and transformer 4|. Thereupon relay l releases, and the subscribers station is res stored to its normal condition.

Should the `absent subscriber return to his telephone -and wish to make use of it while the opcrater is in the act of transmitting messages, he may recover control of his telephone by operating the key 46. The operation of this key opens the printing circuit, allowing the relay 3l to release. The release of relay 3l lights the guard lamp 49 -steadily to notify the operator that the subscriber wishes to use his telephone and she should discontinue the further transmission of mess-ages. Should the subscriber attempt to make use of his telephone without operating the key 46 at a time when messages are being transmitted he would hear a tone through condenser produced by the alternating current flowing in his line and would then realize that the operator was in the act of sending messages to his substation.

The modified substation circuit shown in Fig. 3 differs essentially from the one disclosed in Fig. 1 in that the switching operations are performed by an. auxiliary switch operating motor and by the printery magnet, thus dispensing with the relays 1 land 45 and' with the rectier 6 used in the arrangement of Fig. 1. The small auxiliary motor 62 is connected in parallel with the printer motor 63 and is actuated by the same source of alternating current at the central ofce. The printer magnet 10 and the motor 62 lboth act upon the switch operating spring 66 to control the opening and closing of the associated electrical contacts. When the magnet t6 is rst energized, its armature, acting through the insulating member 1|, urges the spring 66 upwardly out of engagement with contact spring l2 and into engagement with spring i3. The spring 66, however, when thus operated by the full movement o-f the printer magnet armature, does not close the contact springs 68 an-d 69. The motor 62, when energized, rotates a driven member 64 through a small angle, causing the pin 65 to engage the spring 66. The spring 66 when urged by the pin 65 engages insulating member 6l' and flexes `the spring 63 into engagement with contact spring 69. When the spring 65 has been moved into engagement with spring 66, the resistance offered to further movement of these springs causes the motor 62 to stop in its partially rotated position where it remains, as long -as power is supplied to the line, to hold the contact springs in their i closed condition.

The operation of the modified circuit arrange'` ment will now be described. When the 1Z0-volt battery 35 is connected to the tip and ring conductors of the line as hereinbefore described, current flows from this source over the tip conductor 'M through the upper winding '15.of the induction coil, winding of printer magnet l, resistances It and Tl, condenser 78 to ground. The condenser charges; whereupon the control gap of the tube i9 is ionized. An operating circuit for the magnet l' is now closed from conductor 'M through winding l5, magnet 'it through the anode and cathode gap of the tube 'i9 to ground. The printer magnet "nil operates in this circuit and moves the spring 66 out of engagement with spring 'l2 and into engagement with spring '03. The other path of the simplex circuit for the magnet 'It may now be trace-d over the ring conductor St through springs 66 and '13, lower winding 8l of the induction coil, magnet l0, thence through the tube to ground.

The opening of contact springs 66 and l2 disconnects the subscribers telephone $2 from the line, and the closing of springs 66 and 'i3 completes a circuit for supplying alternating current to the motors t3 and t2. This circuit may be traced from the alternating current source at the central office over conductor 'l through the motors 63 and 62 in parallel, springs S and SB and thence over the other line conductor Si). The motor B3 rotates preparatory to the operation of the printer when signals are subsequently received. The auxiliary motor G2 rotates the pin 65 into engagement with the partially operated spring 66, and the spring 66 is now fully operated to close the springs i3 and S9. When the spring 66 is in its fully flexed position the load on the armature of the printer magnet l is removed, leaving the magnet free and unhampered to perform the printing selections when telegraph signals are received. When springs t8 and 69 are closed, the simplex operating circuit of the printer magnet lil is diverted around the tube 19, and the tube thereupon deenergizes. One side of the revised simplex circuit for the printer motor may now be traced from conductor l, winding 75, magnet 76, contacts 69 and 6B to ground; and the other side of the circuit may be traced from conductor 8%), contacts 56 and '13, Winding 8l, magnet springs S9 and 68 to ground.

With this arrangement the substation circuit is prepared by the operation of the printer magnet in response to the initial seizure signal. This initial preparation closes the circuits for supplying alternating current to the printer motor and to the auxiliary motor, the latter of which performs a second switching operation to disconnect the tube and to place the printer magnet circuit in condition for the receipt of the telegraph signals from the central office. The auxiliary motor holds the substation circuits in condition for printing as long as alternating current is supplied over the line. After the messages have been transmitted the substation circuit is restored to its normal condition by opening the alternating current circuit and permitting the auxiliary motor to return to its normal position under the influence of the switch operating spring 66.

if desired, the switching functions performed by the auxiliary motor may be effected by a governor device actuated by the main motor of the printer. Such a device is shown in Fig. 4. When the printer motor SG starts, it operates lever 8l through the governor or centrifugal device 88. Lever 81 operates the switch spring 89 and holds it in operated condition as long as motor 86 continues to run. Spring 89 performs the same switching functions that spring 66 performs in the arrangement of Fig. 3. This arrangement dispenses with the necessity of an auxiliary motor.

What is claimed is:

1. In a telephone system, a central office, a subscribers line terminating therein, said line having a substation thereon, a telephone at the substation of said line normally in operative connection with said line, a message recording device at said substation, means at said substation controlled over said line for rendering said telephone ineiective and for operatively connecting said recording device to said line, a source of current at the central office for operating said recording device over said line, and a signaling circuit including said line for controlling said recording device to record messages.

2. In a telephone system, a central oicc, a telephone line terminating therein, a telephone for said line normally connected thereto, a recording device for said line normally disconnected therefrom, means controlled over said line from the central office for disconnecting said telephone from the line and for operatively connecting said recording device to said line, a source of current at the central oihce for operating said recording device over said line, a signaling circuit including said line for controlling said recording device to record messages, and means responsive to the current flowing over said line from said source for holding said signaling circuit in condition for the transmission of said messages.

3. The combination in a telephone system of a central office, a subscribers line terminating therein, said line having a substation thereon, a printer at the substation of said line normally disconnected therefrom, a space-discharge tube at said substation responsive to a seizure signal transmitted over the line for operatively connecting said printer to said line, a source of current at the central omce for driving said printer, and a signaling circuit including said line for operating said printer from the central office to record messages.

4. The combination in a telephone system of a central oiiice, a subscribers line terminating therein, said line having a substation thereon, a printer at the substation of said line normally disconnected therefrom, a motor for driving said printer, a source of alternating current at the central oilice for operating said motor, a spacedischarge tube at said substation responsive to a seizure signal transmitted over said line, means responsive to the operation of said discharge tube for operatively connecting said printer to the line and for closing a circuit over said line to supply current from said source to said motor, and a signaling circuit including the conductors of said line for controlling said printer to record messages.

5. The combination in a telephone system of a central oince, a Subscribers line terminating therein, said line having a substation thereon, a printer at the substation of said line normally disconnected therefrom, a motor for driving said printer, a source of alternating current at the central ofice for operating said motor, a spacedischarge tube at said substation responsive to a seizure signal transmitted over said line, means responsive to the operation of said discharge tube for operatively connecting said printer to the line and for closing a circuit over said line to supply current from said source to said motor, a signaling circuit including the conductors of said line for transmitting message signals to operate said printer, and means at the substation operated in response to the current flowing over the line from said source of alternating current for maintaining said signaling circuit closed during the transw mission of messages.

6. In a telephone system, a central office, a subscribers line terminating therein, said line having a substation thereon, a telephone at the substation of said line normally connected thereto, a message printer at said substation normally disconnected from said line, an operators position in the central office, means under the control of the operator for establishing a connection from her position to said subscribers line, means at the operators position for transmitting a seizure signal over the subscribers line, means at the substation responsive to said signal for disconnecting said telephone and for operatively connecting said printer to the line, a source of current in the central oilice for driving said printer, a circuit over said line for supplying current from said source to said printer, a signal transmitter at the operators position, and means at the substation of said line responsive to the current flowing thereover from said source for holding said printer in operative connection to said line to receive signals `from said signal transmitter.

7. The combination in a telephone system of a central oilice, a subscribers line terminating therein, said line having a substation thereon, a

printer at the substation of said line normally disconnected therefrom, a character selecting magnet for said printer, a motor for driving said printer, a source of alternating current at the central ofiice for operating said motor, means for sending a signal over said line to energize said magnet, switching means responsive to` the energization of said magnet for closing a motor operating circuit over which current isl supplied from said source to said motor, and means controlled by said motor in response to the flow of current in said motor operating circuit for holding said circuit closed independently of said magnet.

8. The combination in a telephone system of a central oice, a telephone line terminating therein, a printer associated with said line and normally disconnected therefrom, a select magnet for said printer, a motor for driving said printer, a source of alternating current at the central ofce, a driving circuit including the conductors of said telephone line for supplying current from said source to said motor, means for sending a seizure signal over said line to operate said magnet, a switch operated in response to the energization of said magnet for closing the driving circuit of said motor, an auxiliary motor opera-ted in response to the flow of current in said driving circuit for holding said switch in operated position to maintain said driving circuit closed independently of said magnet, and means for sending message signals over said line to operate said magnet.

PAUL VN WELCH.

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