Comtech EF Data SDM-650B - Manual (Page 300)

Trojan Interface SDM-650B Satellite Modem
G–4 Rev. 5
Receiver Ready (RR) indicates that an RF carrier is being received and demodulated with
a sufficiently low error rate for the decoder to remain locked.
The MIL-STD-188-114 interface also provides bi-directional relay loopback of both the
clock and data at the DCE interface. In LOOPBACK from the DTE side, SD is connected
to RD, and either ST or TT (in INTERNAL or EXTERNAL mode) is looped back to RT.
From the modem side, the received data and recovered clock are routed back to the
modulator input for retransmission. During loopback, the synthesizer clock source is
automatically set to Receive Clock for reasons of stability.
Three fault outputs are provided on dry contact Form C relays:
• Common Equipment
• Modulator
• Demodulator
They are available on the FAULT connector on the modem rear panel.
Fault indicators are also provided on TTL open collector drivers on the MIL-STD-188-
114 connector. The TTL MOD fault indicates a MODULATOR fault or COMMON
EQUIPMENT fault, while the TTL DEMOD fault indicates a DEMOD or COMMON
EQUIPMENT fault.