GB431925A - Improvements in or relating to electrical signalling systems - Google Patents

Abstract

431,925. Two-way transmission. ELECTRICAL RESEARCH PRODUCTS, Inc., 195, Broadway, New York, U.S.A.-(Assignees of Jacobs, O. B. ; 20, Hamilton Road, Morristown, New Jersey, U.S.A.) March 5, 1935, No. 6871. Convention date, March 6, 1934. Addition to 412,611. [Class 40 (iv)] In the system of the parent Specification in which the battery supply for the amplifiers at an unattended repeater station is obtained over the line, the repeater station is provided with two complete sets of amplifiers which are energized alternatively according to the direction of the supply current. In Figs. 3 ... 6, each of the pairs of amplifiers 24, 25 and 26, 27 represents a complete set of amplifiers for both directions of transmission, the amplifiers of each set having a common heating circuit from which the grid and anode potentials are derived. In Fig. 3 the heating circuits for the two sets of amplifiers include rectifiers 41, 45 which restrict the supply current to one or the other according to its direction. The supply circuit may be grounded at the repeater by the operation of a relay 40 included in the circuit. When there are two or more intermediate repeater stations relays 40 may be provided at two of them as shown in Fig. 2, so as to divide the repeaters into two groups which are supplied with current from opposite ends of the system and are independently controlled in accordance with the direction of the current. Alternatively, the supply circuit may be connected to one set of amplifiers or the other by a polarized relay 94, Fig. 4, or by a pair of relays 95, 96 Fig. 5, having rectifiers 97, 98 in their energizing circuits. Fig. 6 shows an arrangement similar to Fig. 3 having in addition two further sets of amplifiers 124, 125 and 126, 127 which may be substituted respectively for the sets 24, 25 and 26, 27 by the operation of thermal switches 100, 101. The circuits through the rectifiers 41, 45 both include a polarized relay 104 and a sluggish relay 105, the latter responding to current of normal strength and shunting out 104 but being unaffected by weak current. To replace the amplifiers 24, 25 for example, weak current is sent in the reverse direction so that 104 operates to connect up relay 102 which closes the heating circuit of the switch 100 in series with its second winding and shunts out the amplifiers 24, 25. On the restoration of the normal current the coil 109 becomes heated and melts the solder around the plunger 107 so that it is released and is driven to the closed end of its cylinder, thus connecting in the alternative amplifiers 124, 125. The amplifiers 26, 27 may be replaced in a similar manner. The system is adapted for multiplex carrier working employing different frequency-bands in the two directions and means are described for deriving suitable grid and anode potentials for the amplifiers in the two paths. Specification 381,831 is referred to.