Patent GB-887951-A (GB)
Title: Monitor for the numerical presentation of data
IPC: G06F3/147
Filed: 1959-08-27
Abstract: 887,951. Electric selective signalling. NORTH AMERICAN AVIATION Inc. Aug. 27, 1959, No. 29338/59. Class 40 (1). [Also in Group XIX] The value registered in a binary scale counter 41-50, Fig. 11, forming part of an analogueto-digital converter is read out to an indicating device 933 by inverting the binary number registered and adding one to obtain the complement, entering this value into a counter 879, feeding pulses from generator 971 to counter 879 and to decimal counter 933 until the former returns to zero, the decimal counter then registering the original value in the converter. The invention is applied to the system described in Specification 845,801 in which analogue signals on a number of channels 25 are applied in turn by a multiplexer 15 to the analogue-to-digital converter 18 and the digital equivalents are recorded with the channel number on an output tape. The multiplexer consists of two ten-stage counting rings the outputs from which enable cyclically in turn a hundred diode gates to connect the hundred leads 25 in turn to the converter 18. The number of the channel is supplied from the multiplexer on leads 231 and is recorded with the digital representation of signal strength on the tape. Two sets of ten leads are taken from the multiplexer counting rings to a monitor, one lead being marked in each ten to give the channel connected to the converter at any particular instant. The monitor is adapted to indicate the signal value on a selected lead 25, .the selection being made by two ten-position selector switches 872, 873, Fig. 1, which form a comparator. When the channel counter agrees with the number set up on the switches, a pulse is applied to a complement set trigger 963 so that when a synchronizing signal T12 from a master timer appears, transfer gates 901-910 are enabled to pass to the counter 879 the inverted form of the number in the ten binary stages 41-50 of the converter. The pulse from trigger 963 also passes to a delay unit 992 which, at the end of its delay, feeds a single pulse to counter 879 to add " one " to the inverted form, which is converted thereby to the complement to the capacity of the counters. The delayed pulse from unit 992 also sets a " carry enable " trigger 946 the purpose of which is to delay opening gate 973 until the added " one " has carried as far as necessary through the stages of the counter. When gate 973 opens, pulses from generator 971 (e.g. a free-running multivibrator) pass to counter 879 and to the decimal counter 933 which indicates the count in decimal digits. When the counter 879 has received a number of pulses equal to the number registered in the converter counter 41-50 it reaches its maximum and returns to zero, a zero signal being fed through carry enable trigger 946 to close gate 973. This signal from trigger 946 also passes to a multivibrator 991 which, after an appropriate delay causes a trigger controlled thyratron circuit 953 to reset the counters 879 and 933 to zero. The decimal number is displayed by counter 933 for a period sufficient to be read and is reset before the selected channel is again connected by the multiplexer to the analogue-to-digital converter. The zero condition is held for a sufficient time to enable the operator to be certain the system is working properly by the zero read-out delay 992 which may consist of a monostable multivibrator.