Multidigit code monitoring circuit in PABX exchange - has diode matrix designed to reduce number of columns and number of diodes

摘要

The monitoring circuit, for multidigit codes in PABX exchanges, consists of a matrix with crosspoint diodes. It is designed to reduce the number of columns and therefore the number of diodes. Those columns having a code assigned to them allowing the group to which the code belongs to be recognised are connected to the control input of a bistable flip flop in the evaluation logic. This flip flop drives the logic elements in the evaluation logic in such a way that the logic output (which releases or blocks a connection) is dependent on the group of codes to which the code being monitored belongs.