Clock signal supply

摘要

A clock signal monitor is described having a detector (24-34) responsive to a radio frequency input clock signal to provide a detected signal representative of the amplitude of the input signal. A threshold detector (36, 38, 40) detects whether or not the detected signal represents an amplitude below a threshold. A sounder (42) gives an alarm indication if amplitude below the threshold is detected. If the laboratory reference clock signal becomes weak or fails the alarm indication is given. Equipment's internal reference clock signal generator is generally sufficiently accurate that if incorrectly configured equipment is connected to the laboratory supply, resulting in amplitude modulation of the signal, the beat frequency would normally be around 1Hz. An intermittent alarm indication is thus given at the same frequency as the amplitude of the modulated signal falls below the threshold.