Patent GB-824258-A (GB)
Title: Improvements in or relating to arrangements for measuring arhythmical distortion of start-stop code telegraphic signals
IPC: H04L12/26
Filed: 1955-10-20
Abstract: 824,258. Testing-apparatus for telegraphy. PHILIPS ELECTRICAL INDUSTRIES Ltd. Oct. 20, 1955 [Oct. 23, 1954], No. 30013/55. Class 40 (3). In an arrangement for measuring the distortion in received start-stop telegraph signals, a pulse is applied at each change in polarity of the received signal to the input of a gate circuit having its output connected to a first pulse counting circuit, and at the commencement of the start element a pulse is supplied to operate a second counting circuit and also to render operative a time base circuit which periodically for an adjustable time interval conditions the gate circuit to pass pulses for a number of times equal to the number of elements of a telegraph signal, the repetition period being equal to the duration of an undistorted telegraph signal element. The signals received at terminal K are applied by a bi-stable trigger BS1 through a normally conductive gate P1 to a circuit MS1 which in response to the polarity change at the beginning of the start element of a signal produces a voltage waveform b controlling a multivibrator MV having a natural frequency of 50 c.p.s. and generating a waveform c which is fed back to the circuit MS1 having a fly-back time slightly in excess of 130 m.secs. so that it is returned to normal at 130 m.secs. The waveform c is also applied to mono-stable circuits MS2, MS3 which change their condition and return to their normal state after periods of t1, t2 m.secs. to produce waveforms d, e, which are superimposed in the device AD to produce a waveform f applied to a gate P2 which is closed for a period p extending from 20-t1 m.secs. before to t2 m.secs. after the instants at which signal transitions should correctly occur. The waveform a differentiated at G, is applied to a monostable circuit MS4 having a reset time of 3 m.secs., and the waveform h is again differentiated at D to produce pulses indicated at i which are fed to the gate P2 which passes solely the pulses 3, 5 occurring within the periods r, r<1> outside the permissible range of distortion determined by the interval p. The pulses j are counted in the device TS2, and a counter TS1 to which the waveform b is applied records the number of signals. The outputs of the counters TS1, TS2 are applied to a device BL which is operated after the registration of a predetermined number of signals or distortions to apply a pulse to close the gate P1 to any further signals, and an alarm may be operated when the number of distortions exceeds a predetermined figure. The arrangement may be employed to correlate the number of signals in which distortion has occurred with the number of received signals. The closure of a switch S connects to the gate P2 the output of a bi-stable circuit BS2 which receives the waveform b and is operative by a pulse indicative of a distortion to close the gate P2 to any further distortions occurring during that signal so that the counter TS2 registers the number of signals in which the prescribed distortion has occurred in respect of at least a signal element. The trigger circuit BS2 is restored to normal at the end of each signal by the waveform b.