Comtech EF Data SDM-2020 - Manual (Page 149)

SDM-2020 Satellite Demodulator Revision 4
ASI/RS-422Data Interface MN/SDM2020D.IOM
9–5
9.1.3 User Interfaces
The following paragraphs describe the electrical and physical properties of the ASI/RS-
422 data interface module.
9.1.3.1 Transmit Input Connectors, J3/J4, BNC, Female
These two connectors accept TX data from the terrestrial interface. By default, J3 is
enabled and J4 is disabled. The active input is user programmable and maintained in non-
volatile memory of the modulator or demodulator chassis. Both connectors are terminated
into 75
Ω, whether selected or not.
9.1.3.2 RS-422 Connector, J5, 25-Pin D, Female
This connector is compatible with EIA-530 operation and pin-out. It is a serial interface
with RS-422 signals plus the TTL-OC fault signals indicating the status of the modulator
or demodulator.
9.1.3.2.1 Connector Pinout, J5
The connector is a 25-pin, female, D type, with threaded jack nuts (refer to Table 9-2 for
connector pinout).
Notes:
1. RS-422 signal levels are as defined in RS-422.
2. The differential sense of all signal pairs is a logic “1” when “A” is negative with
respect to “B.”