Specifications

Section 2 — System Descriptions
2.1 General Description
The AFS-3 monitors one or two audio signals and provides a relay contact closure as long as at least one of the audio
signals is present. When no audio is present for a preset period (adjustable from 30 seconds to 5 minutes), the relay
contact opens and remains open until one or both of the audio signals return.
A typical application of the AFS-3 is to provide alternate control for a remotely controlled broadcast transmitter.
When appropriately installed, the AFS-3 can be used to turn off a transmitter by silencing the audio feed to the
transmitter. This procedure would normally be used only when the normal remote control device has failed.
2.2 Physical Description
The AFS-3 is contained in a 19 inch wide rack mounted case, 1.75 inches high. The front panel contains indicator
LED’s and a switch to force closure of the relay contacts and defeat operation of the AFS-3. The rear panel contains
“pluggable” screw-terminal connectors for connecting the audio inputs, power, and relay connections.
Dual-Channel Audio Failsafe model AFS-3
Remote Facilites Controller Accessory
Sine Systems , inc
Enabled AudioPower
Normal
Defeat
Alert
Figure 2.1; AFS-3 front panel
2.3 Electrical Description
2.3.1 Front-Panel Indicators
The front panel of the Audio Failsafe contains four LED indicators:
• "Power" illuminates when the AFS-3 has power
• "Enabled" illuminates when the Normal/Defeat switch is in the Normal position
• "Audio" illuminates when the AFS-3 detects audio
• "Alert" illuminates when the system is in alert condition
2.3.2 Normal/Defeat Switch
The front panel of the Audio Failsafe contains a pushbutton switch. In the Normal position the switch allows the relay
to follow the audio. When audio is present the relay closes (contact between NO and C). When audio is absent for the
preset delay period, the relay relaxes (no contact between NO and C). In the Defeat position, audio is still detected
but the relay is forced into the relaxed position. This logic may be reversed by using the normally closed (NC) contact
in place of the normally open (NO) contact.
2.3.3 Delay Adjustment
The rear panel of the AFS-3 has a rotary switch that adjusts the detection delay. The delay setting determines the
length of time that must elapse for the alert to occur. For example, if the delay is set to 30 seconds then the system
must detect silence continuously for 30 seconds before the alert condition will be triggered.
AFS-3 System Descriptions page 2.1