Comtech EF Data CDM-625A - Manual (Page 169)

CDM-625A Advanced Satellite Modem MN-CDM625A
Front Panel Operation Revision 3
6–43
6.2.1.8.4 CONFIG: CnC
 PMSI-Control
CnC PMSI Mode: Idle
(Idle, Redundancy, Talk, Listen) (
)
The Pre‐Mapped Symbol Interface (PMSI) is an RS‐485 multi‐drop bus system where one device
transmits and all other devices on the multi‐drop bus are configured to receive. Its function, as
associated with DoubleTalk
Carrier‐in‐Carrier, permits the modulator in a selected unit to
provide a direct copy of its output (the outbound interferer) to one or many other modems. The
other modem(s) may then choose to take the PMSI signal and use it for its own CnC reference.
This applies to 1:1 and 1:N systems, and to certain other configurations.
To use this mode of operation, you must connect the appropriate cable to the PMSI connector
on the rear panel of each modem:
 For 1:N multi‐drop applications – Use Comtech EF Data cable P/N CA‐0000275;
 For 1:1 applications – Use Comtech EF Data cable P/N CA‐0000276.
Contact Comtech EF Data Product Support for further details about either cable.
Use the
▲▼ arrow keys to select the desired PMSI control configuration. Press ENTER. Valid
settings are:
Setting Function
Idle Select when CnC is not used.
Redundancy Select when CnC is used in a 1:1 or 1:N redundancy applications.
Talk
Select when CnC is used in other configurations, or for manual testing (the modem will
transmit a copy of its baseband modulated signal on the PMSI port).
Listen
Select when CnC is used in other configurations, or for manual testing (the modem will receive
the PMSI signal, and lock its modulator to this, permitting CnC to use the other modem’s
reference outbound interferer).