Comtech EF Data SDM-650B - Manual (Page 262)

Asynchronous Overhead Channel Unit SDM-650B Satellite Modem
F–4 Rev. 5
F.1.1 Terrestrial Interface
The terrestrial interface (AS/1311) forms the top, when mated with the connector board,
of the 2-board module. The terrestrial interface contains all balanced pair drivers and
receivers for:
• RS-422
• MIL-STD-188
• V.35
Data inputs are send data (SD) and transmit clock (TT or SCTE).
Data outputs are modem reference clock (SCT or ST), receive data (RD), and receive
clock (RT or SCR).
The “handshake” ASYNC signals are:
• Request to Send (RTS)
• Clear to Send (CTS)
• Data
Mode
• Data Set Ready
• Receiver
Ready
• Receive Line Signal Select
This board may otherwise contain circuitry for transformer balanced data interfaces
supporting CCITT G.703 parameters.
Data inputs are Send Data (SD), and outputs are Receive Data (RD).
Data rates of 1.544, 2.048, 6.312, and 8.448 bits/s are supported.
Line codes for zero substitution are B6ZS, B8ZS, AMI, and HDB3. The configuration of
this section is determined at the factory, and is not user selectable in the field.
The ASYNC data channel has three interface options:
• RS-232-C electrical interface allows full-duplex operation.
• RS-485 4-wire also allows full-duplex operation.
• RS-485 2-wire allows half-duplex operation.
These options are jumper selectable. Refer to Figure F-2 for jumper locations on the
interface board. Refer to Tables F-1 and F-2 for jumper configuration information for the
various options and data rates.