12-2. CONTROL
The control module
Monitors
modes.
Monitors
Monitors
Provides
Provides
TM 11-5820-890-30-4
SECTION. Continued
is the LRU controller for the RCU. The control module performs the following functions:
front panel FCTN, MODE, CHAN, and RF PWR switches to provide correct operational
front panel keyboard entries for processing operator inputs.
and outputs the various two-wire link information required by the RT.
serial data outputs for the display and fill routing modules.
a 640-kHz system clock used by other RCU modules.
The two-wire interface provides the two-wire link between the RCU and the RT. Two types of information cross
between the RCU and the RT over the two-wire link. The first type is control information.
When an RT is operated in remote (REM), all of the information normally supplied by its front panel switches
(FCTN, MODE, CHAN, and RF PWR) and its keyboard is provided by the two-wire link. The RCU sends this control
information whenever one of the RCU front panel switches is moved or a keyboard button is pressed. The RT
echoes the control information back to the RCU. When the echo response is not received, OPEN is displayed by
the RCU.
Control information is sent and received by the RCU using frequency shift keying (FSK) in which 2560 Hz is logic 1
and 3200 Hz is logic 0. The two-wire interface converts digital control words from the control module into FSK
signals for output to the RT on the two-wire line. The two-wire interface also receives FSK control information
from the RT, converts it to digital control words, and outputs it to the control module.
The other type of information present on the two-wire link is baseband. Baseband information is voice from a
handset or digital or analog data from a data device. This information is transferred via the two-wire link using a
40-kHz carrier. Digital baseband information is FSK modulated onto the 40-kHz carrier where 45.6 kHz is logic 1
and 34.4 kHz is logic 0. Analog information is FM modulated onto the 40-kHz carrier.
The two-wire interface receives analog baseband information from the ICOM I/O section of the RCU and digital
baseband information from the main switching module. The two-wire interface puts the baseband information on
the 40-kHz carrier and sends it via the two-wire link to the RT for transmission. The two-wire interface also
receives 40-kHz information from the RT, demodulates it, and outputs it to the ICOM I/O section of the RCU.
The main switching module provides control over the routing of the baseband signals within the RCU. It interfaces
with the bit sync switching module to provide many of the same functions of the switching module in the RT. The
main switching module has circuitry that routes digital baseband, PT, or CT (CT always digital) to the two-wire
interface for transmission to the RT. It provides external clock frequencies of 192 kHz, 1.2 kHz, and 150 Hz to the
ICOM I/O section of the RCU. The clock frequencies are derived by a fixed digital divider network from the
640-kHz system clock signal generated in the control module. The main switching module also has an alarm tone
generator used when the RT is in FH mode and a CUE signal is being received.
12-3. ICOM I/O SECTION.
The ICOM I/O section consists of
Circuit Card Assembly
Circuit Card Assembly
Circuit Card Assembly
Circuit Card Assembly
Electronic Component
Circuit Card Assembly
six modules. They are:
- Bit Sync Switching 19A5 (bit sync switching module).
- ICOM Power Supply 19A7 (ICOM power supply).
- ICOM Control 19A8 (ICOM control module).
- ICOM Data I/O 19A9 (ICOM data I/O module).
- Assembly - Fill Routing 19A10 (fill routing module).
- COMSEC 19A11 (COMSEC module).
The module locations are shown in figure 12-4.
12-5
