Code module for subscriber terminals

Abstract

Abstract To monitor the number of outside calls made by each subscriber terminal of a PBX telephone system, each subscriber terminal must be uniquely identified. In accordance with present day practices, PBX systems which have monitoring facilities either perform the monitoring function on the terminal side of the PBX, in which case a large number of monitoring devices are required, or they supply a unique frequency at each subscriber terminal and monitor on the outside trunk line side of the PBX. The use of a separate monitoring function or a separate frequency generator at each subscriber terminal makes the system expensive. The instant invention overcomes these disadvantages by providing a single code module with a plurality of outputs equal at least to the number of subscriber terminals. With these means for identifying the terminals, detectors are required only on the trunk side of the PBX. A code word generator in the module generates a unique code word at each of the module outputs, and each output is applied to a different subscriber terminal. Preferably, the code word generator is a maximal length pseudo-random code generator whose output is serially connected to a long shift register. The outputs of the stages of the long shift register correspond to the outputs of the code word module, and these are connected, in parallel, to the subscriber terminals. A unique code word is generated at each output.

Inventors

• 👤 Solomon Bertram Matthews

Bibliographic Details