GB182867A - Improvements in circuit arrangements for multiplex cable telegraphy and telephony - Google Patents

Abstract

182,867. Gill, H. A., (Deutsche Telephonwerke Ges.). March 15, 1921. Filter, rejector, and separator circuits.- Comprises means of the weatstone-bridge type for filtering or separating currents of different frequencies in a system of multiplex high-frequency cable telegraphy or telephony. In the form shown in Fig. 3, the apparatus comprises four condensers c. c1 arranged in the arms of a bridge, the cable I, II being connected across one diagonal, and the receiving-instrument, or a further series of bridges, being connected across the other diagonal. The condensers are proportioned so that for all frequencies the bridge is balanced, but across opposed condensers are connected inductance coils d with cores consisting of thin axial iron wires. These have the effect of unbalancing the bridge for the lower range of frequencies, which consequently operate the receiver. It is stated that the critical frequency depends on the degree of subdivision of the iron cores. When a series of bridges are employed as shown in Fig. 3, the separation may be carried further, only the lowest frequency ultimately reaching the receiver E. Alternatively, as shown in Fig. 2, the bridge may comprise capacities c1, c2' c3 in three arms and an inductance coil without iron core in the fourth arm; or other arrangements of capacity and inductance may be used in known manner and tuned so as to pass a particular frequency and to transmit all other frequencies to the receiver E. Bridges of this latter type may be arranged in cascade with bridges of the type shown in Fig. 3. Specification 174,312. is referred to.