Instruction manual

G. Supervisor Audio Output: The Supervisor Audio Amplifier combines receive audio with

transmit audio. Transmit audio is derived from sidetone. The level of both signals is set by

the operator for comfortable listening. The amplifier also drives the 100 Ohm Cat 5E cable

to the supervisors panel.

H. Transmit Audio Out: Six buffer amplifiers are used to drive and isolate the microphone

adapters for the various transceivers used. The audio out of these amplifiers is active all the

time and identical. They are not switched with the TRANSMIT switch. Since the outputs of

these amplifiers are biased at +5 Vdc, a coupling capacitor is used to block this voltage.

I. Microphone Logic: The microphone logic routes PTT to the selected transceiver. A ground

is sent to the transceiver selected by TRANSMIT upon PTT.

J. PTT Logic: The PTT Logic block is used to generate discretes needed by the other circuitry.

PTT is inhibited when ICS mode is selected. The PULL discrete is a ground signal to the

Receive Select pull switches that is released on PTT. This signal is sent to Selection Logic

(C). Three isolated PTT inputs are provided.

K. Power Supply: The power supply consists of an input filter, a 10 Vdc regulator and the LED

dimmer circuitry. The input filter is simply a reverse voltage protection diode and a 24V

surge protector diode. The 10 Vdc regulator supplies the DC power for the other circuits in

the Audio Control Unit. The one exception is the ICS circuitry which has it’s own regulator

to handle the power required by the ICS and PA amplifier/drivers.

L. ICS Circuitry. The ICS circuitry includes the ICS circuit board within the Audio Control

Unit and that in the Slideout J-Box (called the ICS J-Box here after). The block diagram of

this function is shown on ACS Block Diagram sheet A4-2.

L1. Call Button Encoder: The call button encoder on the ICS circuit board converts the 6

pushbutton discretes to 3 wire BCD. This is done to reduce wire count between the Audio

Control Unit and the ICS J-Box. The three wires also provide signals to apply power to the J-

box.

L2. Latch & Alert Logic: When the position this ACU is in is being called by another position,

a ground discrete from the ICS J-Box sets a latch in the ACU. The output of the latch enables

the ICS LED blinker and alert tone generator. The LED continuers to blink and a pulsating alert

tone is sent to the headset until the operator acknowledges the call by pulling out on the ICS

knob. At this point, the latch is reset and the alert tone is turned off. The ICS LED becomes

steady on indicating that the ACU is now in ICS mode. The logic sends an “ICS / PA select”

discrete to PTT Logic (J) to inhibit radio transmissions.

L3. ICS / PA Output Amplifier: The ICS / PA output amplifier takes in microphone audio(E)

and sends it to ICS J-box for distribution to other positions if in the ICS mode or the PA system

if selected. The amplifier drives the 100 Ohm Cat 5E cable to the ICS J-Box or PA system.

L4. Power Switch Logic: Since there is no power switch on the Slideout / ICS J-Box, the 3

wire BCD discretes are used to signal the J-Box that another position is powered up and causes

itself to power up. Current flowing in one or more of the 3 wires is enough to cause a power

relay in the J-Box to energize.