Comtech EF Data SDM-650B - Manual (Page 73)

SDM-650B Satellite Modem Configuration
Rev. 5 3–31
3.2.4.9 Specification
Pairs Symmetrical pair, coaxial pair optional.
Circuits Supported SD, RD, MOD FAULT, DEMOD FAULT.
Data Rate 2.048 Mbit/s, ± 50 PPM.
Pulse Width (RD) 244, ± 25 ns.
Line Code AMI or HDB3 (selectable).
RD Amplitude 3.00, ± 0.3V pk into a 120 Ω termination.
SD Amplitude 3, ± 1.5V pk into a 100 Ω termination.
Jitter Attenuation (SD) Exceeds CCITT G.823, specification for 2048 kbit/s.
Modulator Fault Open collector output.
15V max.
20 mA current sink.
Fault is open circuit.
Demodulator Fault Open collector output.
15V max.
20 mA current sink.
Fault is open circuit.
3.2.5 Asynchronous Overhead Interface
3.2.5.1 Functional Description
The asynchronous overhead interface module consists of three subassemblies:
• Connector board is AS/1328.
• Data processor board is AS/1289.
• Terrestrial interface is AS/1311.
Dash # Interface With AUPC
1311-1 RS-422 1311-4
1311-2 V.35
1311-5
1311-3 G.703 1311-6
The connector board provides the physical interface using a 50-pin D connector.
The terrestrial interface contains all circuitry required for G.703, RS-422, MIL-STD-188,
and V.35 type interfaces for synchronous data, and RS-232-C and RS-485 type interfaces
for asynchronous data.
The data processor contains all circuitry required for multiplexing the synchronous and
asynchronous data streams, as well as data rate synthesizers and the optional
plesiochronous buffer.
Refer to Figure 3-12 for a block diagram of the asynchronous overhead interface.