Comtech EF Data SMS-301 - Manual (Page 70)

Theory of Operation SMS-301 Redundancy Switch
4-4 Rev. 3
4.2.4 EIA-422/DVB TX (J1, J2, J3), 25-Pin (PL/6026)
The applications for this switch board are EIA-232, EIA-422, or V.35 format data. The
switch board consists of three 25-pin data I/O connectors, interface, and switching
electronics.
The interface to the M&C motherboard is via a 40-pin connector located along one side of
the switch board. The switch board, under M&C control, will switch data between the
prime modem (J2), and/or the backup modem (J3), and the common customer-data
interface (J1).
The M&C automatically detects the type of switch board installed and presents this
information, via the front panel display, under Interface Type in the Utility System menu.