Transmit Signalling Circuits - Motorola 6864115B62-C Detailed Service Manual

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2.2.3 TX Secure Audio (optional)
The audio follows the normal transmit audio processing until it emerges from the ASFIC CMP TX
SND pin (U0221-44), which is fed to the Secure board residing at option connector J0551-33. The
Secure board contains circuitry to amplify, encrypt, and filter the audio. The encrypted signal is then
fed back from J0551-32 to the ASFIC CMP TX RTN input (U0221-36). The signal level at this pin
should be about 65mVrms. The signal is then routed through the TX path in the ASFIC CMP and
emerges at MOD IN pin 40.
2.2.4 Option Board Transmit Audio
The audio follows the normal transmit audio processing until it emerges from the ASFIC CMP TX
SND pin (U0221-44), which is fed to the option board residing at option connector J0551-33. The
option board contains circuitry to process the audio. The processed signal is then fed back from
J0551-32 to the ASFIC CMP TX RTN input (U0221-36). The signal level at this pin should be about
65mVrms. The signal is then routed through the TX path in the ASFIC CMP and emerges at MOD IN
pin 40.
2.3

Transmit Signalling Circuits

Refer to Figure 4-1 for reference for the following sections.
MICRO
CONTROLLER
U0101
From a hardware point of view, there are 3 types of signalling:
1) sub-audible data (PL / DPL / Connect Tone) that gets summed with transmit voice or signalling,
2) DTMF data for telephone communication in trunked and conventional systems and
3) Audible signalling including Select 5, MPT-1327, MDC, High speed Trunking.
NOTE: All three types are supported by the hardware while the radio software determines which
signalling type is available.
44 HIGH SPEED
19
CLOCK IN
(HSIO)
82
SPI
BUS
85
80 18 LOW SPEED
CLOCK IN
(LSIO)
Figure 4-1 Transmit Signalling Paths
HS
SUMMER
5-3-2 STATE
ENCODER
SPLATTER
FILTER
DTMF
ENCODER
ASFIC_CMP U0221
PL LS
ENCODER SUMMER
ATTENUATOR
THEORY OF OPERATION
TO RF
40
SECTION
MOD IN
(SYNTHESIZER)