PABX telephone network pushbutton dialling circuit - protects multifrequency receiver from interference during dialling and allows extension to receive dial tone

摘要

The pushbutton dialling circuit, for extensions in PABX telephone network coupled to local exchange, protects the multi-frequency receiver from interference during dialling and simultaneously allows the extension to receive the dial tone from the telephone exchange (OVST). After the exchange code has been dialled, the PABX exchange's (NST-ANL) central control (2ST) connects a multi-frequency receiver (MFV-E) and an exchange-line tone generator (425-G) to the extension's (TLN) connection it also connects an exchange-line tone receiver (425-Ee to the local exchange line that the PABX exchange has busied.