GB932502A - Number comparing systems - Google Patents

Abstract

932,502. Comparing digital data. WARNER & SWASEY CO. March 30, 1961 [April 21, 1960], No. 11711/61. Class 106 (1). A circuit for comparing two multi-digit binary numbers R, D, and adapted to provide a first output signal if R > D and a second output signal if R # D, comprises a plurality of stages, each stage being supplied with corresponding digits of the two numbers and with a control signal from the next higher stage. Fig. 3 shows a single comparison stage, the digits R<SP>9</SP>, D<SP>9</SP> being applied at terminals 101, 102 respectively and a control signal from the next higher stage being applied at a terminal 100. Binary " 1 " and " 0 " are represented by high and low potentials respectively. The signal applied at 100 is normally low and is inverted at 112 and supplied via a line 113 to condition an " and " gate 108 which is supplied with digit R<SP>9</SP> and the complement of digit D<SP>9</SP> to provide a high output if R<SP>9</SP> = 1, D<SP>9</SP> = 0, this output being inverted at 130 and applied over a lead 131 to an " and " gate 134 also fed with corresponding leads from the other comparison stages. The line 113 is also connected to "and" " gates 115, 118 supplied with R<SP>9</SP> and the complement of D<SP>9</SP>, the outputs of these " and " gates being supplied to an " or " gate 124 which feeds an inverter 126, the output of the inverter at 127 being connected to the terminal 100 of the next lower comparison stage. The potential at 127 is high if R<SP>9</SP> = 0 and D<SP>9</SP> = 1 or if the potential at 100 is high and in these circumstances the gate 108 of the next lower stage is inhibited so that a high output is applied on the lead 131 of the lower stage. Thus if the higher digits are equal, the corresponding leads 131 are at a high level to condition the " and " gate 134. If at any stage the corresponding D digit is greater than the R digit, the output at 127 of that stage is high to inhibit all the lower " and " gates 108 and cause a high output on their leads 131. The gate 134 is thus opened to produce a high level on a lead 80, which level is also produced if all the R digits equal all the D digits. In all other circumstances the gate 134 is inhibited and the potential on 80 is low. The lead 80 may be arranged to operate a relay (Fig. 1, not shown). The various gates comprise diodes and the inverters triode tubes (Fig. 2, not shown). Reference has been directed by the Comptroller to Specification 836,234.