September 26, 2003
6881096C77-O
3-4
Theory of Operation: W4, W5, and W7 Control Heads
3.1.10 Power On/Off
The HHCH has the ability to turn a host radio on or off by activating S6, which then places a
momentary logic low on the Mic Hi line. This is detected by appropriate circuitry in the host radio,
which then reverses the power on/off state of the radio. Since the microphone power is supplied by a
switched Opt B+ line from the radio, the microphone power on/off state follows that of the radio.
3.1.11 Miscellaneous Functions
If TP1 contacts are momentarily shorted or certain key combinations are pressed simultaneously, the
HHCH is placed in its test mode to carry out various diagnostic checks.
Transient protection diodes D24, D25, D37, D38, and D39 provide electrostatic transient protection
for sensitive components within the HHCH by preventing voltages from going outside the specified
ranges for these components.
3.2
W4, W5, and W7 Control Heads
The following pages describe the operational theory of the components of the W4, W5, and W7
control heads. Refer to
Figure 3-1
for the control-head components.
Figure 3-1. Astro Spectra Control Head Block Diagram
3.2.1
Power Switch/Ignition
For dash-mounted radios, a pushbutton On/Off switch (S1) (or rotary knob on the W4 control head)
on the front panel controls power to the radio and accessories. In addition to this switch, you can wire
the vehicle’s ignition and add or remove control-head jumpers to further control radio operation.
Table 3-2. Types of Operations
Type
How it Operates
Control Head
Jumper/Status
Ignition Wiring
1
RECEIVE and TRANSMIT enabled
via control head ON/OFF switch
(ignition has no effect).
JU1OUT; JU2/IN
Connect ignition cable to
“Battery Hot” at fuse block.
2
RECEIVE and TRANSMIT enabled
only when ignition switch is ON.
JU1/OUT; JU2/IN
Connect ignition cable to
“Ignition” at fuse block.
VOLTAGE
CONVERTER
CIRCUITRY
5 VOLT
REGULATOR
U45
(U3, Q50, T60)
A+/IGN
13.8V
37 VDC
+5 VDC
JU1
JU2
1
2
1
2
A+
IGNITION
U101
VF DRIVER
IC
VACUUM
FLUORESCENT
DISPLAY
U102
34 VDC
2.5 VAC
VIP OUTPUTS
U1
U4
MICRO-
COMPUTER
INTERFACE
AND
WATCHDOG
TIMER IC
SERIAL DATA BUS
VIP INPUTS
IGNITION SENSE
PTT SENSE
HUB SENSE
BACKLIGHT
LEDS
1
2
4.0 MHz
Y1
Содержание ASTRO W5
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