The E2072 is designed to provide sophisticated management of audio sources, such as lines, STLs or onsite backups. The unit detects failures in the composite/multiplex signal used in FM broadcasting and, separately, failures in analogue stereo or AES/EBU digital programme source signals, then, automatically and independently switching to reserve sources. In the case of analogue stereo, when only a single main channel input (left or right) is registered as failed, the remaining good channel is directed to both main inputs (i.e. the source effectively becomes mono).
The time to detect failures and the threshold levels for those failures can be pre-set by front panel controls. As well as signal level, loss of 19kHz pilot in a composite/ multiplex signal, and loss of clock in an AES/EBU digital signal are also detected as failures which cause a reserve source to be selected (though detection of loss of pilot can be disabled internally). The facility to remotely select an alternative Audio main programme source is also provided. Relay outputs are provided for on/off control of reserve programme sources. Front panel displays clearly indicate the status of the switching and settings. Signals present above the set threshold levels are indicated, in real-time, by green displays. The unit uses micro-controller and DSP (digital signal processing) based software control. Comprehensive hardware/ software ‘watchdogs’ are incorporated which illuminate a front panel CPU ALARM display if a software fault occurs. This automatically switches off other front panel displays as their indications may be erroneous in this circumstance and also defaults all path routing relays to select the normal main programme sources (as is the case when the unit is not powered).