Patent GB-412611-A (GB)
Title: Improvements in or relating to telephone and like signalling systems
IPC: H04B3/44
Filed: 1932-12-31
Abstract: 412,611. Two-way transmission. ELECTRICAL RESEARCH PRODUCTS, Inc., 195, Broadway, New York, U.S.A.-(Assignees of Burton, E. T. ; 97, Cypress Street, Millburn, New Jersey, U.S.A.) Dec. 31, 1932, No. 36992. Convention date, Dec. 31, 1931. [Class 40 (iv).] The battery supply for the amplifiers at an unattended repeater station is obtained over the line, and the direction of the current may serve to determine the operative direction of transmission at the repeater. Such a repeater station may be located at the end of a submarine cable, or at an intermediate point in the cable. In Fig. 1, the amplifiers V1, V2 are effective for W-E and E-W transmission respectively. The current supply is obtained from a battery B at a terminal station, and a relay 4 determines the direction of current in the line. As shown, the potential across the small resistance 12 provides a suitable grid bias for V2, while a paralysing negative potential is applied to the anode of V1. When relay 4 is operated by speech arriving at the terminal station, the potential across the resistance 10 provides the grid bias for V1, while V2 is paralysed. A resistance r and condenser c, and if desired an inductance l, are included in the battery circuit to reduce the delay required in the transmitting channel at the terminal station. Fig. 2 shows how several repeaters in tandem may be supplied with current, the circuits through a number of repeaters A being in series in one wire of the line and terminated through a resistance 37 at the repeater B, which receives current from both ends of the line. The repeater of Fig. 1 may be used instead of the repeater B to terminate the series of repeaters A. The grid and anode potentials are such as to render one amplifier operative and the other inoperative. In the repeater of Fig. 3, which may receive current from either or both ends of the line, the supply circuit is shunted across the line through a choke coil 54, the operative condition being controlled substantially as in Fig. 2. The lower speech frequencies are to some extent transmitted conductively through the windings 50, 58, and networks may be inserted to adjust the phase of such frequencies. Attenuation equalizing networks are inserted on each side of the repeater and in the amplifiers. Fig. 5 shows a repeater with hybrid input and output coils, current being obtained from either or both ends of the line over a simplex circuit. Both amplifiers V1, V2 are operative at the same time, anode and grid potentials being supplied from the direct current circuit 71, 84, 83, 85. Figs. 6, 7 show circuits for connecting the end of a submarine cable with a terminal station which may be several miles away over four or three wires, with an amplifier V1 in the receiving circuit from the cable supplied with current over a simplex circuit from the terminal station. Reversal of current renders the amplifier V1 inoperative. Fig. 8 shows an arrangement for cutting out the amplifiers in case of emergency. A relay having two windings 21, 22 shunted across the filaments of the amplifiers V1, V2 is adapted to operate should either of the filaments burn out, thereby releasing a switch 18 which completes a conducting path through the repeater. Alternatively, the relay may be caused to operate by applying an excessive potential at the terminal station to melt fuses 97, 98. The switch 18 in addition operates knives a, b to sever the shunting connections across the line. For submarine locations the repeaters may be sealed in multiple-walled pots with soft wax between the outer walls. The invention is applicable to systems employing carrier frequencies as well as those employing low frequencies.