Comtech EF Data SDM-300A - Manual (Page 214)

SDM-300A Satellite Modem Revision 6
Modem Types MN/SDM300A.IOM
6-6
Asynchronous Overhead with AUPC is a closed network application that gives the user
the ability to communicate from the hub site to the remote site through the added
overhead. The user can use the AUPC feature that remotely controls the remote modem’s
power level, according to parameters programmed by the user. The user can also
remotely monitor and control the remote modem by sending remote commands over the
link via the overhead. This can be done by a local terminal or Monitor and Control
system.
6.1.5 EFD Closed Network Operation
The modem does not require any additional hardware installed to operate in Comtech
EFD Closed Network configuration. The basic modem configuration, which includes the
25-pin D Data I/O connector, supports V.35, EIA-422, and EIA-232 data with no
overhead. The Comtech EF Data closed network configuration allows the SDM-300A to
be compatible with any Comtech EF Data closed network application.
The modem can be compatible with other closed network applications by selecting
different modulator and demodulator types. Fairchild and Comstream compatible closed
network systems can be supported with the modem. When selecting these modulator and
demodulator types, the modem becomes compatible with Fairchild or Comstream closed
network modems that may be at the distant end of the link.
The modem can also support SDM-51 receive-only Remote Space Link Controlled
(SLRC) modems. These receive-only modems are used in closed network applications
where a small amount of overhead is used for monitor and control functions by the
transmitting modem. The modem would become a transmit-only modem when the
SDM-51 compatible modulator type has been selected.
To operate the modem in the SDM-51 compatible configuration, the modem does not
require any additional hardware installed. The 25-pin D Data I/O connector supports
either EIA-422 or EIA-232 data that is used in the SDM-51, SDM-52, or SDR-54
receive-only modems. Refer to Table 6-7 for Comtech EFD Closed Network parameter
settings.