Installation manual

SAFEPATH Manual Sheet 68 of 78
Rev. C April 1999
Supervised Audio System Amplifier/Signal Circuit Module, 40 Watts (SAA)
The supervised audio system amplifier/signal circuit module, 40 watts (SAA) provides audio amplification for the SAFEPATH
system. The amplifier can be selected to have either a 25V or a 70.7V audio output. The amplifier contains a switching power
supply, a linear amplifier, and supervision circuitry.
The switching power supply is used to provide a constant DC voltage to the amplifier while the input voltage is allowed to fluctuate
over its operating range. The amplifier amplifies the low level 600 ohm audio to 40 watts output at either 25V or 70.7V. The
supervision circuit monitors field speaker wiring integrity, field strobe wiring integrity, and amplifier functionality.
The board is capable of being field configured for either 25V or 70.7V output. The configuration is done using a two position slide
switch (S1) on the printed circuit board. One position (the up position) configures the amplifier to have a 25V output and the other
position (the down position) configures the amplifier to have a 70.7V output. See Figure 33 for switch location.
The amplifier supervises both the strobe field wiring and the speaker field wiring with a DC current. The strobe field wiring is
supervised with a reverse polarity technique, which applies a DC voltage with one polarity to supervise the wiring and then reverses
the polarity to energize the strobes. The speaker field wiring is supervised with a DC current which is removed when audio is being
played. Both field wiring circuits are only supervised in the standby state. The amplifier is supervised by monitoring the amplifier
output for audio. The state of each of the three supervision features is indicated via three indicators on the printed circuit board.
See Figure 33 for indicator locations.
There are two fuses on the printed circuit board, F1 and F2. Fuse F1 is the main fuse for the entire board. F2 is the fuse for the
strobe power. See Figure 34 for fuse locations.
Fuse
Rating
F1 10A
F2 3A
Nominal Specifications:
Rated Output @ 1kHz 40 Watts
Input Sensitivity 1Vrms
S/N Ratio 72dB
Frequency Response 275Hz to 4kHz
Input Voltage Range 18 to 30VDC
Supply Current (Standby) @ 24VDC 450mA
Supply Current (Full Load) @ 24VDC 3.8A
Operating Temperature Range 0 to 49 Degrees C (32-120 Degrees F)
Humidity Range 0 to 85%, Non-condensing