Switching procedure for external reference pulse signal in telephone exchange - conducting external reference signals to module delivering reference pulse series for synchronising central pulse generator or clock

摘要

The method enables one of a number of external reference time signals in an exchange system. At least two external reference time signals from external reference sources are passed to the exchange system at at least one reference time supply circuit (LTU4,TMD41) to synchronise central timer (CCG). One external reference signal is selected and switched into the central timer (CCG). A controller (CCGC) allocated to the central timer (CCG) connects a connector lead (LTU4-CCG) between the timer (CCG) and an open switch (S) in the supply circuit (LTU4,TMD41). The central timer (CCG) checks the connected lead (LTU4-CCG) for interference. In the absence of interference the controller (CCGC) closes the switch (S) and thus switches the selected external reference signal to the central timer (CCG). ADVANTAGE - Eliminates interference in synchronising central timer of exchange system.