Comtech EF Data SMS-451 - Manual (Page 34)

SMS-451 Satellite Switch Revision 0
Installation MN/SMS451.IOM
2-8
2.3.1.2 Modem Fault A and B (J8, J9)
The modem fault is provided on a 9-pin female D connector. Modem Fault A and B are
Transistor-Transistor Logic (TTL) inputs from the modem’s modulator and demodulator
TTL fault outputs.
Screw locks are provided for mechanical security on the mating connector.
Pin # Name Function
1 NC NO CONNECTION
2 NC NO CONNECTION
3 NC NO CONNECTION
4 MOD FLT MODULATOR FAULTED
5 GND MODULATOR GROUND
6 NC NO CONNECTION
7 DEM FLT DEMODULATOR FAULTED
8 GND DEMODULATOR GROUND
9 NC NO CONNECTION
2.3.1.3 Receive IF Connectors (J19, J20, J21)
These connectors are the RX IF splitter connectors. The RX IF of the prime modem
connects to RX IF A. The RX IF of the backup modem connects to RX IF B. RX IF
COM connects to the customer equipment. The characteristic impedance of these
connections is 75
Ω (50 Ω optional) from 50 to 180 MHz.
There will be a 3 dB loss between A or B and the COM connector. If the backup or prime
modem is disconnected for any reason, place a 75
Ω or 50 Ω termination on the unused
connector.
2.3.1.4 Transmit IF Connectors (J11, J13, J18)
The TX IF output of the prime modem connects to TX IF “A.” The TX IF output of the
backup modem connects to TX IF “B.” TX IF COM is the transmit IF output connector
and connects to the customer equipment. The TX IF output of the online modem will be
present at this connector. The characteristic impedance of these connections is 75
Ω (50 Ω
optional) from 50 to 180 MHz