Guardian G25AMK005, Technical Manual

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2-18 G U A R D I A N V H F 1 1 0 W M O B I L E
2.7.1 Control Logic Interface
The signals on this interface need not be filtered, but are protected from short circuits to ground. All logic signals
are at 0 to 3V Complimentary Metal-Oxide Semiconductor (CMOS) levels at the interface. The interface carries the
following functions:
•
10V Control
•
Ground
•
/RADON
•
Switched 10V Supply
•
Reset
•
AVR Clock
•
Serial Data Clock
•
Serial Data Input
•
Serial Data Output
•
Key Interrupt
•
LCD Chip Select
•
LCD A0 (data\command select)
•
Keypad Chip Select
2.7.2 Keypad
2.7.3 Switch Interface
Interface to switches is provided to the RECM via 80-pin connector to the Interface board.
2.8 Interface Board
This board is located in the Control Head Assembly in the vehicle cab. The transceiver (RECM) is mounted to this
board and interfaces through 80-pin connector J1. The front panel display PCA mounts to this assembly and
interfaces through 20-pin connector J4. The microphone interface is J5, an 8-pin modular connector.
Communication with the audio amplifier board and the remote RF Power Amplifier is through two 20-pin
connectors J2 and J3. The DC power for this board, the transceiver and front panel functions enters via J3. The 3.3V
powering the display and logic is generated by a linear regulator U1 powered from the 7.8V via an on/off switch
q12. All front panel switches and LED lamps are mounted to this board. Connection to the internal 5W speaker is
via J6.
ON/OFF control : Transistors Q11-14 are connected to the outputs of the binary volume switch SW3. The
transceiver uses these signals to detect the off position of the volume switch. At the off position all lines are open. If
any of the lines is switched and ignition power is high Q17 is on providing low (0V) to one of the transistor witch
will result in a positive ON/OFF voltage. This signal witch is routed also to the audio board to control power
function there and in the remote RF Power Amplifier.
SW4 : Used to change channels. The transceiver uses the binary outputs to detect the position of the channel switch.
Toggle Switches : Program switch SW1 for a variety of functions. Switch SW2 is used to select between internal
and external audio speakers.
Front panel buttons : Keypad depressions on the front panel are detected by the scanning outputs from the
transceiver. Keypad depressions on the optional DTMF microphone are detected by the DTMF decoder on this
board and are processed as ordinary scan-in signals by the transceiver.
DTMF keypad processing : The optional DTMF can be used to program the radio. Keypad depressions generate a
DTMF tone in the audio output. This signal is routed to DTMF detector U6, and digital outputs are sent to1-of-16
de-multiplexer U2. The outputs from U2 are used to control analog switches U3-5. In this way the transceiver scan-
out lines can be connected to the appropriate scan-in lines to simulate a physical switch closure.