GB634369A - Improvements in or relating to apparatus for selecting electrical impulse trains - Google Patents

Abstract

634,369. Electric selective signalling systems. SADIR-CARPENTIER. May 9, 1946, No. 14077. Convention date, May 23, 1945. [Class 40 (i)] [Also in Group XL (b)] A receiver for a telegraph code employing for each character or the like a combination of impulses of two kinds, the number of each kind being fixed, comprises for each character a pair of delay lines, means for applying received impulse trains to one delay line, means for deriving complementary impulse trains in which e.g. marks are replaced by spaces and vice versa, means for applying these complementary trains to the second delay line and a threshold-responsive device connected to taps on both delay lines so positioned that sufficient voltage to operate the device is supplied only for the particular character to be selected. Let us suppose that a threshold relay device 8, Fig. 2, which may be electronic, is required to be operated by the particular signal of Fig. 1a, which is of the type comprising four marks and four spaces, and by no other signal. The signal is received at terminal T, squared at S, and fed to a delay-line 1 which is terminated by its characteristic impedance 2 to prevent end reflection. The line is divided into seven sections by eight taps I ... VIII and the delay of each section is equal to the length of a mark, or space: The taps corresponding to marks in the signal, i.e. I, II, IV and VI are connected by resistors 6 to the relay device 8. Thus, when the first signal impulse reaches tap VIII the remaining impulses will have reached taps I ... VII respectively and there will be a mark, or positive voltage, across each resistor 6. The incoming signal is also fed via a phaseinverter 4 to a second delay line 3 in which the " spacing " taps III, V, VII and VIII are connected via resistors 6 to the relay device 8. Positive voltages will therefore be developed across each of these resistors 6 at the same time as the voltages developed at the first delayline 1. Thus the correct signal will produce a positive voltage at each of eight taps, and the total voltage is sufficient to operate the threshold relay device 8. An incorrect signal will produce zero (or negative) voltage on at least one resistor 6 and fail to operate the relay 8. A similar circuit arrangement is provided for each signal combination which it is desired to receive, but the eight resistors 6 are connected in each case in a manner to correspond with the desired signal. The operation of the relay-device 8 may perform a desired telecontrol operation or signalling function.