Patent GB-434678-A (GB)
Title: Improvements relating to telegraph signalling apparatus
IPC: H04L5/24
Filed: 1934-05-29
Abstract: 434,678. Multiplex telegraphy. HUMBY, A. M., Beam Wireless Station, North Petherton, Bridgwater, Somerset. May 29, 1934, No. 16046. [Classes 40 (iii) and 40 (v)] Relates to double-current cable-code systems in which dots, dashes and spaces are denoted by (++), (--) and (+-) respectively as described in Specification 386,784, and in which the dot-registering means is out of phase with the dash-registering means by half a period, and comprises a system in which a thermionic distributer is employed for applying the signals in one or more multiflex channels to a monitoring recorder or other receiving device. Multiplex signalling. Signals are received by relay RR, Fig. 1, in two channels A, B, Fig. 2, and consist of dots such as 10, dashes such as 17, and spaces such as 18, 22. The two channels are segregated by an armature 4, Fig. 1, controlled by a valve vibrator V1, V2, through amplifiers V3, V4. The movements of armature 4 are shown in Fig. 5 and according to Fig. 1 the B-channel signals are conveyed to a monitoring undulator U while the A-channel signals are suppressed. For this purpose the switch 5 is set upon contact 6, so that when armature 4 is on contact m1 the grids of valves V5, V6 are connected together and the A-channel signals cannot pass to the undulator U. When, however, the armature 4 is on contact S1 the undulator is put under the control of line relay RR and thus receives the B-channel signals. If, however, switch 5 is set to contact 7, the A-channel signals are received and the B-channel signals are suppressed. The vibrator V1, V2 is pulled into step with the received signals by impulses passing through the condenser e. When contact 4 moves to the position in which it renders the valves V5, V6 operative, the armature 8 maintains one or other of the valves V5, V6 in the inoperative state. The other valve, if a dot or a dash is being received, becomes operative after half a signal period, the timeconstants of the circuits R5, C5 and R6, C6 being so dimensioned as to produce this result. Thus dots and dashes are recorded as halfperiod impulses 39, Fig. 4, in the B-channel, while spaces are suppressed, the first and second half respectively of each space being deleted by the persistence of negative charge applied by armatures 4, 8 respectively. Alternatively, there may be an undulator U in each of the channels A and B ; the switch 5 is in this case omitted and additional pairs of contacts are required for the armatures 4, 8, Fig. 6 (not shown). When the signals are applied to an ordinary receiver instead of a monitoring undulator they may be shaped by contactmaking relays or by the application of gridbias to the valves V5, V6. Thermionic distributers. The two-channel distributer comprises the relay CR controlled through amplifiers V3, V4 by a vibrating device comprising valves V1, V2 which are crosscoupled by condensers C1, C2. The vibrator frequency is controlled by varying the resistance Rx in the grid-leak grid-bias circuit, and the vibrations are pulled into phase with incoming signals by impulses applied through condenser e to the grids of both valves V1, V2 at the beginning of each marking impulse.