GB923898A - Improvements relating to electrical signal-separating apparatus - Google Patents

Abstract

923,898. Electric copying machines. FERRANTI Ltd. Aug. 10, 1960 [Aug. 14, 1959], No. 27790/59. Class 38 (6). [Also in Group XL (c)] In a machine tool control system, gating circuits provide for the separation of two pulse signals which are either recorded on a common magnetic track or received from an unspecified source. Four channels are provided, one carrying reference pulses, Fig. 2 (a)R, the other three carrying pulses modulated in phase relative to the reference, in order to control the movements of the machine tool along 3 axes. At intervals, an auxiliary binary coded signal is introduced by either marking or not marking the 3 control signals (and the reference signal if desired) to provide the appropriate code combination. The marking is effected by "notching," Fig. 2 (b) eight successive control pulses in the selected channel by means of auxiliary pulses. For each channel, a reading head 12, Fig. 1, is provided. This controls a bi-stable circuit 14 the output of which is the waveform as originally recorded, Fig. 2 (d). The leading edge of each main pulse triggers a blocking oscillator 15 to generate gating pulses of opposite polarity, Fig. 2 (e) and (f), these pulses being shorter in duration than a main pulse, but long enough to include an auxiliary pulse. Gating the incoming signal at 16 and 17 with the positive gating pulses reconstitutes the main signal free from auxiliary pulses, and gating the incoming signal at 22 with the negative gating pulses produces the auxiliary pulses only, Fig. 2 (h). These are integrated at 23 so that if at least 6 out of the 8 auxiliary pulses are present, a signal is passed via a bi-stable circuit 25 to a binary signal decoder 33. The outputs of the other channels are also applied to decoder 33, provision being made that the arrival of a group of auxiliary pulses in any one of the channels first resets at channels 8 the decoder 33 from its existing reading.