9-9
Section 9-5 - Supervised Audio System Amplifier/Signal Circuit
Module, 40 Watts (SAA-40S)
Wheelock, Inc. Part Number: 105493
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 switch mode 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 module can be 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 (down) configures the amplifier to
have a 25V output and the other position (up) configures the amplifier to have a 70.7V output. See Figure
9-5 on Page 9-10 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 LEDs on the
module. See Figure 9-5 on Page 9-10 for LED 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 9-5 on Page 9-10 for fuse locations.
Two UL LISTED 10K Ohm, 1W, End of Line Resistors are included with this module.
Fuse Rating
F1 10A
F2 3A
Nominal Specifications:
Rated Output at 1kHz 40 Watts
Input Sensitivity 1Vrms
S/N Ratio 72dB
Frequency Response 275Hz to 6kHz
Input Voltage Range 24VDC
Supply Current (Standby) at 24VDC 400mA
Supply Current (Full Load) at 24VDC 3.6A
(Including 2.0A Strobe Current)
Operating Temperature Range 0 to 49 Degrees C (32-120
Degrees F)
Humidity Range 0 to 85%, Non-condensing
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