Emergency; Mechanical On/Off; Ignition; Hook Rss - Motorola GM-950 Manual

2.4

Emergency

The emergency switch (J0400-9), when engaged, grounds the base of Q0441 and pulls the line
EMERGENCY CONTROL to low via D0441. 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 go low (0.2V), thereby setting the EMER IGN SENSE line to low.
While EMERGENCY CONTROL is low, SW B+ is on, the microprocessor starts execution, reads
that the emergency input is active through the voltage level of EMER IGN SENSE, and sets the B+
CONTROL output of the ASFIC pin B4 to a logic high. This high will keep Q0611 switched on. This
operation allows a momentary press of the emergency switch to power up the radio. When the
microprocessor has finished processing the emergency press, it sets the B+ CONTROL line to a
logic 0. This turns 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 already be high.
2.5

Mechanical On/Off

This refers to the typical on/off button, located on the control head, and which turns the radio on and
off. If the radio is turned off and the on/off button is pressed, line ON OFF CONTROL goes high and
switches the radio on as long as the button is pressed. The microprocessor is alerted through line
ANALOG 3 which is pulled to low by Q0925 (Control Head with display) while the on/off button is
pressed. If the software detects a low state it asserts B+ CONTROL via ASFIC pin B4 high which
keeps Q0611, and in turn the radio switched on.
If the on/off button is pressed and held while the radio is on, the software detects the line ANALOG
3 changing to low and switches the radio off by setting B+ CONTROL to low.
2.6

Ignition

Ignition sense is used to prevent the radio from draining the vehicle's battery because the engine is
not running.
When the IGNITION input (J0400-10) goes above 6 volts Q0611 is turned on via line IGNITION
CONTROL. Q0611 turns on SW B+ and the microprocessor starts execution. A high IGNITION input
reduces the voltage of line EMER IGN SENSE by turning on Q0450. The software reads the line
EMER IGN SENSE, determines from the level (Emergency has a different level) that the IGNITION
input is active and sets the B+ CONTROL output of the ASFIC pin B4 to high to latch on SW B+.
When the IGNITION input goes below 6 volts, Q0450 switches off and R0449, R0450 pull line
EMER IGN SENSE high. The software is alerted by line EMER IGN SENSE to switch off the radio
by setting B+ CONTROL to low. The next time the IGNITION input goes above 6 volts the above
process will be repeated.
2.7

Hook RSS

The HOOK RSS input is used to inform the µP when the Microphone's hang-up switch is engaged.
Dependent on the radio model the µP may take actions like turning the audio PA on or off.
The signal is routed from J0101-3 and J0400-14 through transistor Q0101 to the K1µP U0101-23.
The voltage range of HOOK RSS in normal operating mode is 0-5V.
Theory of Operation
Open Controller
5C.3-3