Patent GB-393633-A (GB)
Title: Improvements in or relating to volume control arrangements for telephone or like signalling circuits
IPC: H04B3/20
Filed: 1931-12-09
Abstract: 393,633. Two - - way transmission. ELECTRICAL RESEARCH PRODUCTS, Inc., 195, Broadway, New York, U.S.A.- (Assignees of Wright, S. B. ; 310, Western Drive, South Orange, New Jersey, and 'Taylor, E. R. ; 114, West 70th Street, New York, both in U.S.A.) Dec. 9, 1931, No. 34187. Convention date, Dec. 10, 1930. [Class 40 (iv).] In a system -comprising a two-way circuit coupled to two one-way circuits, as in telephony with a radio or submarine cable link, adjustable controls being provided for varying the sensitiveness of the voice-operated relays and the signal volume in both one-way paths, the signal volume in one path is varied automatically in accordance with the other adjustments. The invention may be applied to the automatic control of the transmitting volume, but in the system described the automatic control is of the receiving volume. General operation. The lines L1, L2 lead to a wireless transmitter and receiver respectively and are coupled over the circuit TL to any of a number of toll and local lines. An operator, by means of switches B, C, D controlling variable loss networks, adjusts the transmitting volume and the sensitiveness of the voiceoperated relays. When the sensitiveness (in decibels) of the transmitting relay exceeds that of the. receiving relay by an amount in excess of the sum of the losses inserted by both volume controls, the return loss of the particular telephone line connected at the moment and the fixed losses between the two amplifierdetectors, signals received may be too weak to operate the receiving relay but may operate the transmitting one, and to avoid this any of the adjustments by the switches B, C, D necessitates an adjustment of the receiving volume control. This adjustment is normally made automatically but, if the key Sw is thrown, is made by means of the manual switch A in response to telltale signals the operation of which is described below. Automatic control of received volume ; telltale signals. Each of the adjustments referred to varies the amount of resistance in a control circuit comprising marginal relays R, R<1> with different margins (fixed by biasing windings). When the received volume is correct, R<1> only is operated and telltale lamps S1, S2 are dark When the volume should be reduced, both relays pull up, S2 glows, and 12 (or 22, depending on the previous setting of the control relays) pulls up. 12 energizes 11 which puts in the first step of the received volume controlling network, and 13 which energizes R5. R5 breaks the control circuit and energizes R6 which opens the circuit of 12 which therefore falls followed by 13, 11 however remains locked in series with R4 which operates sluggishly, further breaks the circuit of 11, and releases the relay corresponding to the 0 position of the volume control. If the received volume is still too great the relapse of R5, R6 following that of 13 causes the operation of 22 and the locking of 21 to put in the second step of the loss network. If the received volume can safely be increased, R, R1 are both deenergized, S1 glows, and a circuit is made for 22 or 12, according to whether 31 or 21 is operated to put in the preceding step of the loss network. Variations in accordance with characteristics of two-way circuit. The switch J is used to cut resistance, characteristic of the return loss of the two-way circuit in use, into the control circuit. In the case of toll calls, battery is put on TL, R7 cuts out a fixed-loss pad in the two-way circuit and R8 inserts a loss-pad in the path of 'the receiving amplifier detector AD2 and alters the hang:over time of the receiving relay R3. In some circumstances WH<1> may be thrown to prevent the operation of R8 and in some KH may be thrown to make a different adjustment of the hang-over time of R3 and to energize R9 which cuts a fixed loss pad into the path to AD2.