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RBSU/RBSS Interface Units

The RBSU provides an optional backup power supply, R40S, that will supply backup power to TE 
devices in the event of an AC power loss. This power backup option only applies to RBSU or 
RBSS circuits that are configured in the NT mode. See 

 to install the R40S.

Also the Strata CTX system must have battery backup to allow the R40S power backup function to 
operate. The R40S power supply is an ISDN, PS-1 type power unit which means it supplies power 
to TE devices on the RBSU/RBSS transmit and receive wire pairs as shown in 

. This 

power arrangement is also known as phantom power.

Each of the four circuits on RBSU/RBSS can be connected to share the R40S using option 
switches on the PCBs (see 

). Before using the R40S as a backup power source, make sure 

the TE devices do not require more power than the R40S can supply and the TE is compatible with 
the ISDN PS-1 power arrangement.

³

Run all ISDN programs related to RBSU/RBSS BRI circuits prior to installation of the PCBs. 
This enables the circuits to operate immediately upon insertion. ISDN BRI programs are 
explained in the Strata CTX Programming Manual under the ISDN tab.

³

Set all option switches and jumpers on the RBSU and RBSS PCBs before plugging the RBSS 
onto the RBSU or inserting the RBSU into the system. RBSU/RBSS switch/jumper 
information and locations are shown in 

 and 

4774

TE Device
Power sink

R40S PS-1
Power
Source

RJ45 Pin Nos. on
RBSU or RBSS
NT circuit

RJ45 Pin Nos.
on TE device

R40S Power Limits:
Voltage: 33.3VDC to 38.85VDC maximum
Current: 100mA maximum (25mA maximum per each RBSU/RBSS circuit)