Redbox User Handbook No 1
101
9 RB-SD1 Silence Detection Unit
Introduction
Fig 9-1: RB-SD1 Front Panel
The RB-SD1 Silence Detect Unit is a 1U rack mount device used to monitor an unattended
stereo studio feed and in the event of the signal going “quiet” after a given period the
unit will switch through an alternative stereo audio signal. This signal could be a recorded
message (e.g. “normal service will be resumed”, etc), a feed from a CD player or minidisk
machine, or an alternative recorded program. Controls are provided to start external
equipment and to provide remote status indication.
It has 2 balanced stereo audio inputs with the maximum input level being +28dBu. Each
input is user-defined as either the main source or auxiliary source and both sources
are monitored for failure, each having a remote failure alarm. In the event of the main
source dropping below a pre-set level for a pre-determined amount of time, the unit will
automatically switch through to the auxiliary signal. The silence detect level is adjustable
between -60dBu and -15dBu in 3dB steps via a 16 position rotary switch on the rear panel.
The silence interval can be adjusted between 2 seconds to 30 seconds in 2 second steps,
or, alternatively, set to 2 minutes 5 seconds also via a 16 position rotary switch on the rear
panel. The audio outputs use stereo professional balanced XLR-3 male connectors.
The unit can operate in 2 modes - automatic or manual. In both modes it will automatically
switch over to the auxiliary source on detecting silence. When the main signal is again
detected it will either return to the main signal automatically or manually depending on the
mode chosen.
The RB-SD1 has a number of remote operational features. Remote outputs provide separate
relay contact closures for failure of the main and auxiliary inputs. You can also control
remotely all of the front panel switches for source selection, mode selection and signal
Restore. You can remotely start and stop another piece of equipment on alarm failure
and main signal return respectively. Also, the longest silence time (2min 5sec) can be set
remotely, which is useful if you are expecting to broadcast a long silence.
The unit can be configured to alarm when either the left or right channel of the main input
source fails, or if the whole stereo signal fails. There are also options to set the remote start
output as momentary or latched, to disable switching to the auxiliary input on alarming
and to increase the gain on the auxiliary input so that an unbalanced input can be used, for
example, from a domestic minidisc player.
Front panel LED indicators show individually left and right programme and alarm conditions
for both the main and auxiliary inputs. The status of the source, mode and alarm state are
also shown on the front panel with LED indicators.
SY
NCHR
ONISERS, DEL
A
Y
S & SILENCE DE
TEC
TORS - RB
-SD1
SYNCHRONISERS, DELAYS &
SILENCE DETECTORS
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