External Alarm; Rssi Buffer - Motorola M11URD6CB1_N Service Manual

Theory of Operation
Controller Audio & Signaling Circuits

External Alarm

For External Alarm installations, switch S401 (1-3)
should be ON. This pulls the analog switch control line
U402-9 low, and the switch positions of U402 are as
shown in the schematic. When the radio's alarm mode
is enabled and the proper code has been received,
ASFIC port U201-A3 goes high, turning on Q411 via
U402-(11-13) and R411, saturating Q411 and pulling
J400-4 low.
For External Alarm installations, switch S401 (1-3)
should be OFF. This pulls the analog switch control line
U402-9 high via R442, and the switch positions of U402
are the opposite from those shown in the schematic.
Data Modem
For Data Modem installations, switch S401 (1-3) should
be OFF. This pulls the analog switch control line U402-
9 high and the switch positions of U402 are thrown
opposite of that shown in the schematic.
NOTE
All Data Modem I/O functions are active
low, 0 VDC.
The reconfigured pin functions of accessories connec-
tor J400 are as follows:
J400-12 is an input to the radio which allows the data
modem to mute the radio's speaker audio while data
bursts are being received. The modem pulls J400-12
low, which is routed through switch U402 from pin 14
to 1, and turns on Q415 and, therefore, Q401. This pulls
U401-8 low, muting the audio power amplifier.
J400-4 is an output from the radio which tells the
modem that the radio is transmitting by pulling J400-4
low. Two non-simultaneous conditions are summed to
8-16
GTX LTR/Privacy Plus 800 MHz Mobile Service Manual
recognize transmit mode under all timing conditions.
If PTT is low, Q410 is off and a high is provided via
R440, D403, U402 pins 12-13, and R411, to turn on Q411
and pull J400-4 low. If the transmit-enable voltage
K9V1_ENABLE is high, a high is provided via D403,
U402 pins 12-13, and R411, to turn on Q411 and pull
J0400-4 low.
J400-15 provides system busy indication by observing
the status of the AUDIO_PA_ENABLE line, which is
low during active receive conditions. This low is pro-
vided to J400-15 via D402, indicating a signal is being
received.
J400-3 is DATA_PTT input to the radio, routed via
switch U402 pins 4 to 3, to U101-8. The ASFIC (U201) is
configured for FLAT_TX_AUDIO when DATA_PTT is
asserted at U101--8.
J400-5 provides a FLAT_TX_AUDIO input to the radio,
via C418 and gain-reduction buffer U202 (pins 1, 2, 3),
to U201-D7. This connection is always provided and is
not reconfigured by the setting of switch S401 (1-3).
J400-11 provides a Flat/Unmuted RX Audio Output
from the radio. This audio is obtained directly from
detector U5201-28 via C230 and R236, is routed from
U402 pin 10 to pin 5, amplified by U403 and applied to
J400-11 via R419 and C419.

RSSI Buffer

For special applications, a DC voltage proportional to
received signal strength can be provided to J400-15.
This requires removal of resistor R430 and diode D402,
and insertion of resistor R215. The DC signal-strength
voltage is provided by detector U5201-11, buffered by
U202 (pins 12, 13, 14), and routed via R215 to J400-15.
6880905Z99-O June, 2000