Comtech EF Data CRS-120 - Manual (Page 16)

1:1 Redundancy Switch Revision 3
Introduction MN/CRS120.IOM
1–2
IMPORTANT
The 1:1 redundancy switch does not support switchover of data circuits.
Accordingly, a 1:1 system comprises an Online Modulator, a Standby Modulator, and the 1:1
redundancy switch Switch.
WARNING
Note that the 1:1 redundancy switch was designed specifically as
an accessory product for the CEFD CDM-710 Satellite Modem,
equipt as a Modulator, and is not intended for use with any other
manufacturer’s equipment.
IMPORTANT
Read this specification in conjunction with the specifications for the
CDM-710 , as details of the operation of that equipment is not covered
in this document.
1.2 Description
The 1:1 redundancy switch connects two modulators, an Online unit and a Standby unit. It
monitors the fault status of these two units, and controls the routing of IF signals though the
controller from the two units. When there is an equipment failure, switching automatically takes
place to protect the IF traffic circuit. Figure 1-2 illustrates the 1:1 redundancy switch connected in
a 1:1 application with two modulators.
The 1:1 redundancy switch derives its operating power from the two modulators - Online and
Standby. A diode sharing arrangement, with a current sharing circuit ensures that in normal
operation power is taken equally from the two modulators. However, in the event that one of the
two units is removed, the remaining unit supplies the entire current requirement. The Modulators
supply +12 volts DC individually up to160 mA max. The modulators employ electronic fuses,
which prevent excessive current from being drawn by the 1:1 redundancy switch, should an
anomalous condition occur.