GB369630A - Improvements in telephone and telegraph transmission systems - Google Patents

Abstract

369,630. T w o way transmission. STANDARD TELEPHONES & CABLES, Ltd. and THOMAS, P. R., Columbia House, Aldwych, London. Dec. 23, 1930, No. 38664. [Class 40 (iv).] In a telegraph and telephone transmission system wherein the direction of telegraph transmission is under the control of speech, means are provided to prevent operation of the telegraph transmitter until its circuit is in condition for transmission. The Figure shows the terminal equipment at one end of a cable c, the branches L<1>, L<2>, TL<1>, TL<2> being respectively the telephone and telegraph transmitting and receiving branches. The telephone and telegraph signals are separated by filters Fl, F2. When speech arrives on line L<1>, the output of the amplifier is divided between the delay network D and detector AD<2> which operates relays S<1>, S<2>, S<3>. Relays S<1>, S2 connect the telephone and telegraph transmission lines to the cable c and relay S<3> which is slow to operate effects a delay in the operation of the telegraph transmitter TT until after the line TL<1> is connected to the cable C in order to prevent loss of signal during the switching period. In order to prevent both terminal stations being operated simultaneously to transmitting positions, a pulse of tone or other current may be transmitted during the delay period of speech to disable the equipment at the distant end.