4: Theory of Operation
4-10
TW7201I-MS
4.4
7000RI Option
The 7000RI option is the remote control DHSL Modem board in the
transceiver. The 7000RI DHSL Modem board must be installed in a TW7000
or TW7000F transceiver to communicate with the TW7201I remote head.
The 7000RI consists of an DHSL Modem board installed in the transceiver’s
FSK/DHSL slot. It also includes a serial dual UART chip and two jumpers
that configure the transceiver’s processor. On the transceiver Processor board,
jumpers must be installed on jumper/headers JU11B and JU12A.
The DHSL Modem board interfaces with the Front Panel Processor board
through connectors J11 and J12 (J1 is not used in the transceiver DHSL
Modem board).
4.4.1
Power and
Ground
Power and ground are routed to the modem board through the J11 connector.
Connector J12 provides the remote line interface through the DC regulation
and interface board; it also connects to the Processor board. Connector J1 is
not used on the 7000RI DHSL Modem board. Connector J11 connects to the
Audio board, and the DC regulation and interface board. Voltage regulators
U14 (5 Vdc), U17 (8 Vdc) and U12 (9 Vdc) provide regulated power to the
various circuits.
4.4.2
BITE Circuitry
The BITE circuit consists of transistors Q4 and Q5. The 5V supply keeps Q5
biased on whenever the DHSL Modem board has power. If the DHSL Modem
board loses power, Q5 turns off and Q4 turns on (active low) to indicate a
BITE failure to the processor. Converter U1 output QB is set low to disable
the BITE for certain tests.
4.4.3
Modem Clock
Crystal oscillator Y1 (4.096 MHz) and associated logic (U10F, U10E, U10D,
U8 and U9) generate the modem clock that provides timing to the modem IC
U6, codec IC U11 and the two data set interfaces U3 and U4.
4.4.4
RS-232
Interface
The RS-232 interface is available for the remote control head DHSL Modem
board but not the 7000RI DHSL Modem board.
4.4.5
Codec
The codec U11 is a voice digitization and reconstruction device. In transmit
mode, the 7000RI uses the codec to digitize an audio signal from the front
panel microphone or an external microphone connected to one of the rear
panel accessory connectors. The codec sends the transmit audio to the DHSL
modem U6 to transmit to the TW7201I through a 2-wire remote cable.
Summary of Contents for TW7201I
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