Meter for remote monitoring of sound levels

摘要

The sound level meter is installed in a case with the control and communications circuits. It is linked to a remote central computer via a modem and the telephone system. It has an internal back-up power supply which comes into operation if the local mains supply fails. In this event a fault signal is sent to the computer. Internal switches detect tampering with the unit or its microphones. Ultrasonic signals are used to determine if the microphones are covered up. The central system makes regular automatic check calls via the modem to ensure that the telecommunications link is in working order.