The AG-738 audio detector is designed to be used to
detect the presence of a stereo program signal and
provide alarm outputs on failure of the left, right or
both channels and of stereo phase reversal.
Alternately the AG-738 can be used to monitor two
mono audio circuits and provide individual alarm
outputs on failure of a audio circuit.
The AG-738 will accept audio signals in the range -
20 dBm to +20 dBm from a balanced or unbalanced
source, presenting an input impedance of 10 kOhms.
The detector circuitry consists of precision rectifier
circuits driving comparators. These enable oscillators
to trigger dual monostable circuits allowing the
response time of the alarm circuits to be set.
The detection threshold of each channel is adjustable
within the range of –20 dBm to +20 dBm. |
The response time is set by means of DIP switches in
the RC timing circuit and is adjustable from 5 to
160 seconds for the AUDIO FAIL time out and 5 to
40 seconds for the AUDIO PRESENT response time,
the adjustment being made in 5 second steps.
The alarm circuitry consists of latching circuits
triggered by the detector circuits. These drive two
relays whose contacts are available at the rear panel
of the AG-738.
The alarm circuits can be reset automatically upon
return of the audio signals or by a contact closure
from the front panel or a remote circuit.
Visual indication of the state of the AG-738 detector
and alarm circuits is provided by LED indicators on
the front panel. |
