ANALOG TRANSMIT SIGNAL PATH. Continued
In CT analog transmit, the XMT ANLG output is routed to the COMSEC module. In CT, RCV PT/CT SEL/R is a Iogic
1, which grounds out the XMT PT ANLG/R path in the ICOM controI moduIe and ICOM power supply. XMT ANLG is
input to an analog-to-digital converter inside the COMSEC module. The digital signal is then encrypted and output
on the TDCT line. The XMT ANLG input is also switched to the AUDIO RCV output and routed to the ICOM control
moduIe as sidetone. TDCT is routed to the main switching moduIe, where it is summed with XMT PT DGTL and
output on the PT/CT DGTL OUT line. PT/CT DGTL OUT is routed to the two-wire Interface, where it is FSK
moduIated onto the 40-kHz carrier for transmission to the RT. The 40-kHz A/D SEL line is set to a logic 0 by the
control module selecting the PT/CT DGTL OUT line. The control module monitors the XMT DGTL MODE-N output
of the main switching module to determine the correct setting of the 40-kHz A/D SEL line. XMT DGTL MODE-N is
a logic 0 in transmit CT, transmit PT digital, and TF.
The COMSEC module outputs PT/CT SEL/R and PTTR/PTTO are input to the main switching module and cause the
RCV PT/CT SEL line to go to a logic 1, grounding the switches in the ICOM controI module and ICOM power
suppIy. PTTR/PTTO transitions to a logic 0 when the TDCT line becomes active after COMSEC PTT-N is applied.
This activates the RADIO PTT-N output of the main switching moduIe.
12-10. DIGITAL DATA RECEIVE SIGNAL PATH.
All received digital data is FSK moduIated onto the 40-kHz carrier by the RT, demodulated by the two-wire
interface, and is output on the 40-kHz XMT DATA line at Iogic 0/1 Ievels. See figure FO-22. The bit sync switching
module synchronizes the 16 kb/s PT digitaI signaI with the 16-kHz CLOCK and outputs it on the BIT SYNC DATA
line. Both of these lines are inputs to the main switching module. BIT SYNC DATA is output as RCV PT DGTL. The
16-kHz CLOCK is output on the PT DGTL CLK Iine when ACQ/TRK #1 is a logic 1, indicating synchronization, AUD
MOD DDMC-N is a logic 0, and PT is seIected. AUD MOD DDMC-N is a Iogic 0 when digitaI data rates or TF is
seIected. A 192-kHz CLK is aIso output when low speed data rates or TF is selected. RCV PT DGTL, PT DGTL CLK,
and 192-kHz CLK are buffered by the ICOM power suppIy and input to the ICOM controI moduIe.
The 40-kHz XMT DATA output from the two-wire interface is also input to the COMSEC module for the processing
of received 16 kb/s CT digital signals. The received CT digital data is synchronized to a local cIock, decrypted,
and output as DDR in conjunction with the synchronized cIock, DDC. DDR and DDC are input to the ICOM
control module for data rate processing.
The received PT signals (RCV PT DGTL/R and PT DGTL CLK/R) or the received CT signaIs are seIected for
processing internal to the ICOM control moduIe by the RCV PT/CT SEL/R Iine. RCV PT/CT SEL/R is set to a Iogic 1
(CT) when the CDSQ-N output of the COMSEC moduIe is a Iogic 0, indicating successful decryption. RCV PT/CT
SEL/R is set to a Iogic 0 (PT) when CDSQ-N is a logic 1. When the data rate is set to 16K, received data and the
digital clock are routed straight through the ICOM control module to the RCV DATA OUT and RCV CLK OUT
outputs. When TF or low speed data rates is selected, the received data and received clock are routed to the
data rate adapter inside the ICOM control module. The data rate adapter looks for the PT or CT code word placed
on the message by the transmitter. If the code word is not detected, the data rate adapter sets switch controI
lines to enabIe the receive audio path for voice reception. if the code words are detected, the data rate adapter
converts the 16 kb/s signal to the low speed data rate. The data rate adapter also de-exclusive ORs PT digital
messages. Low speed digital messages and the low speed clock are also output on the RCV DATA OUT and RCV
CLK OUT lines. The low speed clock is derived from the 192-kHz CLK/R input. Converted TF data is output on the
SEQ DR DC OUT line.