Charger Led Indicator Drivers; Vrs/Pac•Rt Control; Dc Switches - Motorola Astro XTS Instruction Manual

Charger LED Indicator
Drivers
VRS/PAC•RT Control

DC Switches

22
Whenever the portable radio is turned on, R93, VR30, and R55 provide
bias voltage (+9 Vdc) to the microphone (J4 pin 5) and supply to the
multiplexer (MUX) (U2). Transistor Q5 conducts when driven by
transistor Q18. Transistor Q18 monitors the radio's OPT B+ line and
drives Q5 when the radio is on.
Transistors Q10 and Q11, display LED drivers, conduct for particular
charger conditions. They are driven by signals from microprocessor U5.
Transistor Q11, through current-limiting resistor R87, controls the green
illumination of LED D1. Transistor Q10, through current-limiting resistor
R86, controls the red illumination of LED D1. Similar transistors Q16 and
Q21 control the radio mode LEDs in D2
Dimmed LED illumination is controlled by XTVA installation wiring
to the vehicle headlight switch. When conditions are dark, LED
brightness is reduced by headlights on. The headlight A+ signal at J2
pin 4 operates Q22, causing conditions through dual diodes D12 and
D13, and resistors R209 through R212. Voltage at driver transistor
bases becomes reduced, causing lower LED current when on.
LED disabling (typically custom installation for surveillance
operation, for example) operates by grounding connector J5, pin 13
through diodes D10 and D11, causing driver transistor bases to be
taken below 0.7 Vdc.
The XTVA circuit board includes a vehicular repeater system (VRS)
control circuit, consisting of transistor Q15 and associated circuitry.
Transistor Q6 monitors the presence of a radio in the XTVA console.
When the radio is inserted into the XTVA console, Q6 stops
conducting, causing Q15 to conduct. This logic low is routed to the
VRS output to control the VRS; its internal pullup resistor enables the
VRS. It is recommended that the installer include a user switch across
this output to VRS to provide a user-selectable VRS disable. The closed
setting of the switch is used when the vehicle (so equipped) is in the
out-of-service condition, such as off duty.
To minimize vehicle battery current drain, the XTVA is designed to
disconnect itself from vehicle supply when not in service. XTVA
subcircuits become powered on-demand only (see Table 3 on page 23).
In summary:
• If no radio is loaded, all circuits are turned off.
• If a radio is loaded but not turned on (provided the ignition
switch is ON), only the charger section turns on when it detects a
radio battery in the charger pocket.
• If a radio is loaded and turned on, all audio circuits turn on.
• In addition (provided the ignition switch is ON), the XTVA
includes a time-out function which allows the charging circuit to
continue to operate for 1/2 hour after the ignition is switched off.