Specifications

External Channel Unit SDM-309B Satellite Modem
C-C–16 MN/U-SDM309B Rev. #
2.1.2 Connector Pinouts
The RS422 and MIL-STD-188-114 interface is provided on a 37 pin female “D”
connector accessible from the rear panel of the modem. Screw locks and latching blocks
are provided for mechanical security of the mating connector.
Signal Function Name Pin Number
SIGNAL GROUND SG 1, 19, 20, 37
SEND DATA SD-A
SD-B
4
22
SEND TIMING ST-A
ST-B
5
23
RECEIVE DATA RD-A
RD-B
6
24
REQUEST TO SEND RS-A
RS-B
7
25
RECEIVER TIMING RT-A
RT-B
8
26
CLEAR TO SEND CS-A
CS-B
9
27
DATA MODE DM-A
DM-B
11
29
RECEIVER READY RR-A
RR-B
13
31
TERMINAL TIMING TT-A
TT-B
17
35
MOD FAULT _ 3
DEMOD FAULT _ 21
MASTER CLOCK
(INPUT)
MC-A
MC-B
16
34
2.1.3 Specification
Circuit Supported SD, ST, TT, RD, RT, DM, RR, MOD
FAULT, DEMOD FAULT, MC
Amplitude (RD,RT,ST,DM,RR)
4 ± 2 V differential into 100 !
DC Offset (RD, RT, ST, DM, RR) 0 ±.4 V
Impedance (RD,RT,ST,DM,RR)
Less than 100 !, differential
Impedance (SD,TT,MC)
100 ± 20 !, differential
Polarity True when B positive wrt A
False when A positive wrt B
Phasing (RD,RT) False to True transition of RT nominally
in center of RD data bit.
Symmetry (ST,TT,RT) 50% ± 5%
Frequency Stability (ST) ± 100 ppm
Modulator Fault Open collector output
15 V max
20 mA max current sink
Fault is open circuit
Demodulator Fault Open collector output
15 V max
20 mA max current sink
Fault is open circuit