Specifications

Generally, the most desirable location to "tap" the audio signal for use by the AFS-3 is a point where the signal level is
somewhere between 0 dBm and +10 dBm. This could be the output of a discrete STL, the output of audio processing
equipment, or the transmitter's audio input terminals. Telephone line audio is not a good source for the AFS-3 since
the audio level of telephone lines is generally about -30 dBm. The output of a processing device would be a good
monitoring point in such installations. The audio input impedance of the AFS-3 is approximately 50 KΩ so bridging the
AFS-3 across a program source usually has no significant effect.
After installing the AFS-3 make sure that the "Audio" LED does in fact turn off when audio is lost. Otherwise the
timing interval will never begin and the AFS-3 will not work as intended.
3.2.4 Delay Adjustment
The period of time required after the loss of audio before the alert condition is triggered is set at the factory to 2.5
minutes. This can be adjusted with the 10 position rotary switch on the rear panel of the AFS-3. The adjustment
range is 30 seconds to 5.0 minutes in 30 second increments.
NO C NC 12VACA- A+ Gnd B+ B-
Dual-Channel Audio Failsafe model AFS-3 • Sine Systems, Inc. • Nashville, Tennessee
Audio Inputs
Sine Systems , inc
Relay Out • Power
2.5
2.0
1.5
1.0
0.5
3.0
3.5
4.0
4.5
5.0
Delay Adjust
(minutes)
Figure 3.1; AFS-3 rear panel
3.2.5 Relay Connections
The contacts of the internal relay are accessed through the terminals labeled "Relay Out" on the rear panel. As
shipped from the factory the output relay contacts are dry and can be used to make/break contact in an external
circuit. When audio is present the normally closed (NC) and common (C) terminals make contact. When the failsafe
is in alert condition the normally open (NO) and common (C) terminals make contact.
!
Although the relay contacts are rated at 120 volts AC, it is not recommended that 120 volts AC be
connected to the AFS-3. The screw-terminal connectors have several exposed points that could produce
a dangerous or even lethal shock if they were contacted. Low voltage AC or DC is much safer and
eliminates the potential for a shock hazard.
AFS-3 Installation page 3.2