Electronic On/Off; Emergency; Mechanical On/Off; Ignition - Motorola GTX/LCS 2000 Service Manual

Electronic On/Off

Emergency

Mechanical On/Off

Ignition

Diode D5601 located on the PA section acts as protection against transients and
wrong polarity of the supply voltage.
The radio has circuitry which allows radio software and/or external triggers to turn
the radio on or off without direct user action.
Some examples of where this is useful are: 1) automatic turn on when emergency
switch is engaged; 2) automatic turn on when ignition is sensed and off when
ignition is off.
Q0611 is used to provide SW B+ to the various radio circuits. Q0611 acts as an
electronic on/off switch controlled by Q0612 (the switch is on while Q0612 is on).
When the radio is turned on, the voltage at the base of Q0612 is high (about 0.6
V). Q0612 switches on (saturation) and pulls down the voltage at Q0611-base.
This turns on Q0611 and supplies SWB+ to the radio. The on resistance of Q0611
is very low (less than 1 Ω), so the voltage level at SWB+ is quite the same as A+.
The electronic on/off circuitry can be enabled by the microprocessor (through
ASFIC, line B+ CONTROL), the emergency switch (line EMERGENCY
CONTROL), the mechanical On/Off button on the control head (line ON OFF
CONTROL), or the ignition sense circuitry (line IGNITION CONTROL). If one
of the 4 paths cause a low at the collector of Q0612, the electronic ON process is
engaged.
The emergency switch, when pressed, grounds the base of Q0441 and pulls the
line EMERGENCY CONTROL to low. EMER IGN SENSE is pulled high by
R0441. When the emergency switch is released, the base of Q0441 is pulled high
by R0442. This causes the collector of transistor Q0441 to drop down (0.2 V),
thereby setting the EMER IGN SENSE line to low.
While EMERGENCY CONTROL is low, Q0611 is turned on, SW B+ is enabled,
the microprocessor starts execution, reads the voltage level of EMER IGN SENSE
line, and sets the B+ CONTROL output of the ASFIC to a logic high. This high
level keeps Q0611 switched on through Q0612. This operation allows powering
on the radio by a momentary press of the emergency switch. When the
microprocessor has finished processing the emergency press, it sets the B+
CONTROL line to a logic 0. This cuts off Q0611 and the radio turns off. Notice
that the microprocessor is alerted to the emergency condition via line EMER IGN
SENSE. If the radio was already on when emergency was triggered, then B+
CONTROL would have already been at a high level.
This refers to the typical on/off button which is located on the control head and
turns the radio on and off. While the on/off button is turned on, line ON OFF
CONTROL goes high during the short pulse generated by the ON_OFF "one-
shot" circuitry in the control head. This switches the radio on. The microprocessor
is alerted through line ANALOG 3 which is pulled to low by Q0925 (Control
Head P+) while the on/off button is turned on. If the software detects a low state,
it asserts B+ CONTROL via ASFIC-GCB2, which keeps Q0612 and Q0611on,
and in turn the radio is switched on.
While the on/off button is turned off, the software detects the line ANALOG 3
changing to low and switches the radio off by setting B+ CONTROL to low.
Ignition sense is used to prevent the radio from draining the vehicle's battery while
the engine is not running.
Theory of Operation 7-9