Untitled record

Application filed. November 24, 1926. Serial No. 150,496.

This invention, relates to. two-way telephone systems, and more particulary to two-way telephone systems including a fourwire circuit having-paths adapted for transS mission in opposite directions and a combined wire and radio circuit having outgoing and.Incoming wire paths connected·,to the four-wire circuit.

The object of the invention is the min10 imitation of the false operation .of echo sup pressors in the circuits byr noise or static entering the wire sections of tlie system from the radio link.

Tiiis object is -attained.by providing for 15 the disabling of the incoming wire path of the combined wire and radio circuit in response to currents of a given value or a greater value m the corresponding outgoingwire path, and regulating the currents lipw20 ing over the outgoing path so that they will always have a value sufficient to effect the disabling of the incoming path.

My invention will be more clearly understood when the following description and 25 discussion are read with reference to the accompanying drawing, which shows in diagrammatic form- a telephone system to which the. invention is applicable.

At the left of the drawing there is shown 10 an ordinary four-wire circuit equipped with one- way repeaters or amplifiers. This .fourwire circuit is connected at A to the two-wire line L_x with the usual hybrid coil and balanc-. ing network. This four-wire circuit,; .fur35 thermore, is equipped with the ordinary echo suppressor apparatus. The W—E ampifierdelector, -operated by outgoing currents, controls the incoming transmission path through the operation of the relay R_r40 Biimlarly, the E—W amplifier-detector, operated by currents in the incoming path, controls the transmission over the upper path by the operation of the relay R₂.

Between the four-wire circuit and the dis45 taut two-wire line L₂ there is shown a combined wire and radio circuit. The two-wire sections of this circuit are joined by.the radio link, as shown. The left-hand wire section of the combined circuit, which will be 50 given closer consideration, is connected at C to B of the four-wire circuit by a cord circuit repeater connection or by other suitable connection, the usual hybrid coils and balancing networks being included. The outgoing ⁶⁵ connection to the radio link is through the radio transmitting apparatus at D, and the incoming radio waves are received at E. Tlie distant wire link shown at the right of the drawing has corresponding radio receiving and transmitting apparatus and the «ο usual one-way repeaters or amplifiers, and is connected to the two- wire line L₂ through the usual hybrid, coil and with the usual balancing network. The amplifier-detectors of the four-wire circuit, shown-at the c>5 left of the drawing, are usually adjusted so that full operation will not be obtained at all times, since the volume of transmission which may be applied to the two . terminals of the four-wire circuit;varies over 70 a considerable range. Hence at times—-for instance, if a weak talker is talking through A over the outgoing transmission path—the W—E. amplifier-detector will fail to operate. Th. is condition is practically satisfac- 75 tory provided that the noise interference, is no greater than that ordinarily received from wire lines._:

If, however, the four-wire circuit, is connected to a combined, circuit including a 80 radio link, the interference from noises .or static may be great, sufficient to upset, the proper operation of the echo suppressor devices. More specifically, the E—W amplifier-detector may be operated by the interfer- 85 ing currents at a time when a weak talker through A has not control of the circuit due to the fact that the voice currents are too weak to operate the W—E amplifier-detector. In such a case it is obvious that the 90 outgoing transmission from A is seriously interfered with.

The section of the combined wire and radio circuit between C and D and E is shown equipped with echo_: suppressor and singing 95 suppressor apparatus. The W—E amplifier detector of this section of the circuit is operated by . outgoing currents in the upper wire path. The outgoing transmission path is normally blocked in front of the radio 100 transmitter at D, being short circuited. When the W—E amplifier-detector operates, it clears the outgoing transmission path, the operation of the relay R₄ removing the short circuit; it also disables the, incoming trans- 105 mission path through the operation of the relay R_n, which places a short circuit on the incoming path. The E—W amplifier-detector of this section of the circuit operates on currents in the incoming path to place a ^no

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Q short circuit on the outgoing path through the operation of the relay R₅.

It is obvious, upon an examination of the circuit, that clipping will, result unless the ₅ W—E amplifier-detector of the combined circuit functions without fail; that is, there must be full operation on the outgoing.transmission path. It is also obvious that an irregular operation of the corresponding E— j₀ W amplifier-detector, such as might be caused by noise or static coming in at E, will prevent the clearing of the outgoing transMission path unless control of that path is assured by tlie certain functioning of the I;-, W—E amplifier-detector. To take a specific case, a weak talker through A must be able to control the transmission path through D in spite of the interfering noise or static re eived 'at E.

The problem outlined above is solved by adjusting the W—E amplifier-detector of tlie combined circuit so that it will operate at a given value of the outgoing currents in the wire, section or at a greater value, and 2.-, the value of these outgoing currents is regulated so that it will always be sufficient to cause the full operation of the amplifierdetector. A suitable means for attaining the desired result is a .regulating network 30 N which should be placed in the outgoing path before the one-way repeater or amplifier P.

By the method described above, even a weak talker through A is enabled to control gj the outgoing transmission-path. His voice may not be strong enough to operate the echo suppressor on the four-wire circuit, but the voice currents in the outgoing wire path of the combined wire and radio circuit will be 40 regulated so that full operation of the W—E amplifier-detector of the combined circuit will be obtained. Thus the outgoing path is cleared, and static or noise entering at E is prevented from hindering the clearing of 45 the outgoing path or blocking that path through the operation of the relay R₅. Also, of course, currents due to noise or static entering the path EC, are prevented from beingpassed on to the incoming path BA of the four-wire circuit and, falsely operating the 50 E—W amplifier-detector. of that circuit.