A method of monitoring the frequency stability of an oscillator used for network element clock generation and generating an alarm indication

摘要

The method involves subtracting an output value of counters by a subtractor (S). An output signal of the subtractor is filtered by a digital high pass filter (DHPF). An output signal of the DHPF is rectified by a rectification module (ABS). The output signals are compared if the output signal of the module is greater than a specified value. An alarm indication is created if output signal is greater than the specified value. An independent claim is also included for a circuit for monitoring frequency stability of an SDH network equipment clock generator fixed frequency local oscillator (LO) and for generating an alarm indication (Al) in case the frequency drift or fluctuation of the local oscillator (LO) exceeds a specified value.