Patent GB-788993-A (GB)
Title: Improvements in or relating to number comparators
Inventor: WRIGHT ESMOND PHILIP GOODWIN
IPC: H04L12/54
Filed: 1954-01-15
Abstract: 788,993. Code telegraphy. STANDARD TELEPHONES & CABLES, Ltd. Jan. 15, 1954, No. 34911/55. Divided out of 788,991. Class 40 (3). [Also in Group XIX] An arrangement for determining the highest of a plurality of numbers comprises means for comparing a succession of numbers in turn with one of said numbers until a number is found higher than that used as the bases for comparison, after which further numbers not yet compared, are compared with the said higher number, and the process is continued until the highest of the plurality of numbers has been determined. The arrangement may be modified to determine the lowest of a plurality of numbers, or to determine the equality or otherwise of code combinations of binary digits. The subject-matter is wholly included in Specification 788,991 and is employed in a telegraph exchange system in which incoming messages are recorded on a magnetic track on a beam and transferred to one or more storage tracks provided in common for all the incoming message tracks. At the time of transfer, information concerning a message, such as its priority, is recorded on a carrier track and then transferred to a booking track on which the relevant information including the priority criterion, is set up in time sequence as the messages are received. The arrangement described is utilized to detect from the booking track the message of the highest priority so that its disposal can be effected in the correct order of precedence. The information on the booking track is passed to a register 111B, the priority being registered in binary code on the elements 111R1 ... 111R5. The number with which comparison is to be made is registered on the elements 112R1... 112R5 on the register 112R and since initially this will be zero, the first comparison will provide a positive output TS which is generated whenever the number recorded on 111R is greater than that set up on 112 R. The arrangement described is restricted to priority number 0 ... 7 which are set up on the elements 111R3 ... 111R5 and 112R3 ... 112R5 and it can be verified that with the arrangement of gates G1106-G1113, a positive pulse TS is derived from the gate G1113 when the number on 111R3 ... 111R5 is greater than that on 112R3 ... 112R5. If the numbers registered on 111R3-111R5 and 112R3- 112R5 are equal, an inverter 111X produces a positive pulse CPS. The positive pulse TS is effective to operate a position register, Fig. 2 (not shown), which provides an output 101f4 effecting in conjunction with an appropriate waveform IPC and pulses tl, t2, derived from the storage track, the transfer of the booking information to 112R. The comparison is carried on until the highest priority has been found and transferred to the register 112R and when, by the continuation of the examination of the booking track, this numeral has again been registered on 111R3 ... 111R5, the positive pulse CPS steps the register of Fig. 2 (not shown), so that the recording is erased from the booking track and subsequently from the register 112R, but not before the operator's track selector has found the storage track or tracks on which the message of the highest priority has been stored, and has associated this track with a teleprinter at the operation position for reproducing the first line of the message which is to be passed to its desired destination.