Comtech EF Data CRS-500 - Manual (Page 40)

CRS-500 1:N Redundancy System Revision 2
Introduction MN-CRS500
1–14
1.3.3 CRS-282xx IF Switch Unit (ISU)
The CRS-282xx ISU is intended for use with the CDM-625 modems in 1:N redundancy when the
Traffic modems within the redundancy group connect to more than one transponder or
different polarizations of the same transponder.
The ISU is available in separate Tx and Rx units for a variety of connector and IF Band
configurations (50Ω or 75Ω 70/140MHz, or 50Ω L-Band):
CRS-500 1:N Redundancy System ISU Options
ISU Type Model No. CEFD P/N Frequency, Impedance Connector
Transmit
CRS-282T50 PL-0000460 70/140 MHz, 50Ω BNC female
CRS-282T75 PL-0000592 70/140 MHz, 75Ω BNC female
CRS-282TL PL-0000454 L-Band, 50Ω Type ‘N’ female
Receive
CRS-282R50 PL-0000462 70/140 MHz, 50Ω BNC female
CRS-282R75 PL-0000593 70/140 MHz, 75Ω BNC female
CRS-282RL PL-0000456 L-Band, 50Ω Type ‘N’ female
Each ISU is constructed as a 2RU-high, rack-mounting chassis designed for mounting into the
rear or top of a 19-inch rack. It is provided with rack handles at the front for easy removal from
and placement into a rack.
When the entire group of modems is connected to the same transponder, you may bypass using
the CRS-282xx IF Switch Unit and, in its place, passively combine or split the modulator outputs
and demodulator inputs. In these applications, the CRS-500 mutes the offline modem’s Tx
carrier and enables the online modem’s Tx carrier.
Up to four ISUs may be connected to the CRS-500 Redundancy System to enable the Redundant
Modem to back up the failed Traffic Modem for either 70/140MHz and/or L-Band.