Audio Failsafe Model AFS-3 – INSTALLATION AND OPERATION – This documentation is valid for Audio Failsafe hardware version 3.0 and software version 1.
Table of Contents Section I – Safety Information / Warranty 1.1 Safety Information Page Number 1.1 Section 2 – System Descriptions 2.1 2.2 2.3 2.3.1 2.3.2 2.3.3 General Description Physical Description Electrical Description Front Panel Indicators Normal/Defeat Switch Delay Adjustment 2.1 2.2 2.1 2.1 2.1 2.1 Section 3 – Installation 3.1 3.2 3.2.1 3.2.2 3.2.3 3.2.4 3.2.5 3.2.6 3.2.7 3.2.8 3.2.9 3.2.
Section 1 — Safety Information 1.1 Safety Information ! The AFS-3 Audio Failsafe should be installed only by qualified technical personnel. An attempt to install this device by a person who is not technically qualified could result in a hazardous condition to the installer or other personnel, and/or damage to the AFS-3 or other equipment. Please ensure that proper safety precautions have been made before installing this device.
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.
Section 3 — Installation ! The AFS-3 Audio Failsafe should be installed only by qualified technical personnel. An attempt to install this device by a person who is not technically qualified could result in a hazardous condition to the installer or other personnel, and/or damage to the AFS-3 or other equipment. Please ensure that proper safety precautions have been made before installing this device. 3.1 System Includes The Audio Failsafe package contains these items: • • • 3.
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.
3.2.6 Logic Voltage Output If the AFS-3 will be connected to an external sensing device, there are jumpers inside the AFS-3 that can be set so that the output relay switches a logic voltage to indicate an alert condition. Jumper positions JP2-4 set the logic voltage output. No jumpers are installed at these positions at the factory and the relay contacts are dry--no voltage. JP4 places +5VDC (current limited throuh a 2.2K pull up resistor) on the common (C) relay contact.
3.2.9 Power Supply Loss Note that if power is lost to the AFS-3 the output relay will relax because there is no voltage to energize the coil. Additionally, there will be no logic voltage output since there is no power supply. Consider this and take necessary steps if it becomes necessary to disconnect power from the AFS-3. ! 3.2.10 Safety Considerations If the AFS-3 is connected so that loss of audio turns a transmitter off, the return of audio could turn the transmitter back on.
Section 4 — Circuit Description and Repair 4.1 Circuit Description The first two sections of U1 are balanced audio input stages of the "A" and "B" audio inputs. Overall, these have a gain of 0.33 (loss). The next stage combines the two channels and has a gain of 10. Capacitors C1 through C12 provide high frequency roll-off and RFI immunity. A rectifier, short term integrator (about 1 second), and comparator follow. When audio is present, the "Audio" LED is turned on by this comparator.
4.2.3 Factory Service Policy Sine Systems is proud to offer same day repair service on all of our products. When we receive damaged equipment, we will repair it and ship it back the same day it arrives. Because we offer immediate service, we do not send loaner equipment. If we cannot immediately repair equipment and return it, we may ship a loaner unit at our discretion.
All repairs must be billed to a credit card or shipped COD. Specify which you prefer with your request for service. At your request, we will call with the total amount of the repair (including applicable shipping charges) so that suitable payment can be arranged before a COD shipment. If you need a COD total, do not forget to include a telephone number where you can be contacted. 4.2.
Section 5 — Specifications 5.1 General Operation Output relay contact closes (NO and C connected) within one second after audio becomes present and remains closed as long as audio is present. Output relay contact opens (NC and C connected) at the end of an adjustable delay period after audio becomes absent. Delay Range 30 seconds to 5.
5.5 AFS-3 Component Layout Specifications page 5.
5.6 Parts List (hardware revision 1.00) Quantity Part Description and Value AFS-3 board, PC, AFS-3, Rev. 1 1 capacitor, aluminum, radial, 1,000 µF, 25v 1 capacitor, aluminum, radial, 10 µF, 16v/short 1 capacitor, aluminum, radial, 100 µF, 16v/short 1 capacitor, monolythic ceramic, 0.1 µF, .1" spacing 1 capacitor, monolythic ceramic, 100 pF, .1" spacing 4 capacitor, monolythic ceramic, 1000 pF, .1" spacing 4 capacitor, monolythic ceramic, 27 pF, .1" spacing 2 capacitor, polyester, 0.
Quantity Part Description and Value AFS-3 resistor, SIP, 7 x 4.7K, common 1 socket, DIP, 14, 1 socket, DIP, 20, 1 switch, cap for C&K latched pushbutton, light gray, round 1 switch, DIP, rotary, 10 position, front adjust 1 switch, pushbutton, latched, DPDT, PCB, 90° 1 transformer, wall plug, 12V AC, 1.
