Patent GB-621723-A (GB)
Title: A system for transmitting telegraph signals on electric waves
IPC: H04L7/02
Filed: 1938-08-23
Abstract: 621,723. Copying telegraphy ; telegraphy. HUDEC, E. Aug. 23, 1938, Nos. 24753, 24754, 24755, 24756 and 24757. Convention dates, Aug. 26, 1937, Oct. 12, 1937, Dec. 10, 1937, Dec. 23, 1937, and Jan. 5, 1938. [Class 40 (iii)] Telegraph and like signals are changed into pulses occurring at the beginning, or the beginning and the ending, of the signal, which are keyed on a carrier wave for transmission and at the receiver are changed back into the original signals. The signal a, Fig. 4, is applied at u, Fig. 5, and differentiated by the transformer M to give the pulses b, Fig. 4. The carrier wave is keyed by the first pulse to transmit a pulse corresponding to the beginning of the signal a. If pulses occurring at the beginning and the ending of the signal are required to be transmitted, the signal a, Fig. 4, is applied at u, Fig. 6, the valves 2, 3 being controlled respectively by the positive and negative pulses b of Fig. 4 to produce unidirectional pulses in R for keying the carrier. The pulses preferably have a duration of <1>/1000 second. Where pulses b, Fig. 1, are transmitted at the beginning of each signal a, the receiver has a local oscillator generating pulses c corresponding to the ending of each signal a; the pulses c are applied at u2, Fig. 2, to act in the opposite direction to pulses b applied at u1, so that the discharge device K is rendered conducting by a pulse b and non-conducting by a pulse c, thus reconstituting the signals a; in this arrangement, further pulses must be transmitted after the beginning pulse if the telegraph signal is a long one, the further pulse co-inciding with and opposing the locallygenerated pulse to maintain K conducting. The discharge device K may be grid-controlled, Fig. 14 (not shown), or controlled by two valves fed in opposite phase by the received and locally-generated signals. For copying telegraphy, the transmitted signals are developed as in Specification 507,912, Figs. 7 and 19 (not shown). The locally-generated pulses c, Fig. 9, may coincide with the beginning of the telegraph signal and the transmitted pulses correspond to the end of the telegraph signal. In Fig. 10, the locally-generated pulses c either start or maintain the developed telegraph signals, while the received pulses terminate the telegraph signals. In Fig. 11, the locally-generated pulses c generate a continuous train of pulses, the received pulses b interrupting this process either to maintain or inhibit a telegraph signal. The locally-generated pulses may be of great amplitude, Figs. 20, 21, 22 (not shown). In a modification, the transmitted pulses are produced by integration; the telegraph signals are applied to the valve V, Fig. 16, to render it conducting and charge condenser C until its potential allows current to pass through glow discharge device K, and the charging current through R drops; the device K becomes non- conducting when the signal ceases, so that the current through R consists of short pulses occurring at the beginning of each signal. An inductance can be used instead of a condenser, Fig. 17 (not shown). According to the Specification as open to inspection under Sect. 91, when pulses are transmitted at the beginning and ending of each signal, the received pulses are applied at U, Fig. 4 (Cancelled), the first pulse rendering the glow discharge tube K conducting, thus altering the bias on the valve V so that the next pulse renders the valve conducting to quench the discharge in K, the telegraph pulses being developed across R4. This subject-matter does not appear in the Specification as accepted.