Alert Tone Circuits; Accessory Connector Configurations; Remote Desk Set; Public Address - Motorola M11URD6CB1_N Service Manual

GTX LTR/Privacy Plus 800 MHz Mobile Service Manual
iters for PL and HS data. The hysteresis of these limit-
ers is programmed based on the type of received data.
NOTE
During HS data, the µP may generate a
sampling waveform seen at U0201-G1.

Alert Tone Circuits

When the software determines that it needs to give the
operator an audible feedback (for a good key press, or
for a bad key press), or radio status (trunked system
busy, phone call, circuit failures), it sends an alert tone
to the speaker.
It does so by sending SPI BUS data to U201 which sets
up the audio path to the speaker for alert tones. The
alert tone itself can be generated in one of two ways:
internally by the ASFIC, or externally using the µP and
the ASFIC.
The allowable internal alert tones are 304, 608, 911, and
1823Hz. In this case a code contained within the SPI
BUS load to the ASFIC sets up the path and determines
the tone frequency, and at what volume level to gener-
ate the tone. (It does not have to be related to the voice
volume setting).
For external alert tones, the µP can generate any tone
within the 100-3000Hz audio band. This is accom-
plished by the µP generating a square wave which
enters the ASFIC at U201-C3.
Inside the ASFIC, this signal is routed to the alert tone
generator; the output of the generator is summed into
the audio chain just after the RX audio de-emphasis
block. Inside U201 the tone is amplified and filtered,
then passed through the 8-bit digital volume attenua-
tor, which is typically loaded with a special value for
alert tone audio. The tone exits at U201-J4 and is routed
to the audio PA like receive audio.
Accessory Connector Configurations
The configuration of the pins of accessory connector
J400 can be changed to support different accessories by
changing the settings of dual switch S401.
S401 (pins 2-4) is turned ON if external Ignition Sense
is not used, and turned OFF if an external Ignition
Sense cable is installed. The operation of the Ignition
Sense circuitry is described above in the "Electronic
On/Off" and "Ignition" sections of the Controller
Detailed Functional Description.
S401 (pins 1 and 3) is turned ON to support Remote
Desk Set, Public Address and External Alarm, and is
turned OFF to configure the accessory connector for
External Data Modem applications.
June, 2000
The radio is shipped with Ignition Sense
disabled and Remote Desk Set, Public
Address and External Alarm enabled.

Remote Desk Set

For Remote Desk Set applications, 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. The PTT signal from the desk
set at U400-3 is routed via U402-4 and 2 and via U203 -
1 and 2 (U203 is ON since pin 4 is high via R433 and
R431) to µP port U101-22. The hook signal at U400-14 is
inverted by Q101 and applied to µP port U101-23.
Transmit audio at U400-2 (EXTERNAL_MIC_ AUDIO)
is connected in parallel with the front panel mic audio
input and applied to ASFIC U201-B8. DC bias required
by microphone is provided by R204 and R205.
GATED_RX_AUDIO which is de-emphasized and
controlled by the squelch mute gate is obtained from
ASFIC U201-H5, buffered and amplified by U403 and
sent to the desk set at J400-11.

Public Address

Public address operation requires an accessory
HLN9322 Public Address Switch Box and one or more
HSN1000 amplified speakers. In the Public Address
mode, the radio functions simply as a junction box
which routes microphone audio from the front panel
connector directly to the switch box via J400-2, where it
is further amplified and routed to the amplified speak-
ers. Additionally, the microphone PTT does not key the
transmitter, and the microphone off-hook condition is
ignored, appearing to be on-hook.
For Public Address operation, 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 Public Address mode is turned
on using the Switch Box, the switch box pulls J400-12
low. This signal is passed through switch U402 from
pin 14 to 15, which also goes low. The hook line is
pulled low by D401, forcing the microphone to appear
on-hook. The control line to gate U203-4, normally
high via R433, is pulled low, turning off U203 and pre-
venting MIC PTT from being applied to the µP. Thus,
microphone audio is routed to the public address
speakers but the radio does not transmit, and receiver
operation is maintained in the same condition it was
when the microphone was on-hook.
SW_B+ from J400-9 is supplied to the switch box,
where it powers the internal amplifier stages and also
turns on a rely which applies battery voltage to the
external amplified speakers. Thus, when the radio is
turned off, all PA circuits and amplified speakers are
turned off as well.
6880905Z99-O
Theory of Operation
Controller Audio & Signaling Circuits
NOTE
8-15