INSTALLATION
6.Check that all cables are labeled.
INSTALL EMERGENCY TRANSFER UNITS (ETUs)
The 106 Emergency Transfer Unit (ETU) (Figure 2-32)supports up to five Power Failure Transfer (PFT) sets and a DID make-busy function. Up to four ETUs can be supported for a maximum of 20 PFT sets. The sets can be connected to selected loop-start or ground start trunks. PFT sets must be FCC registered single-line sets. If ground start trunks are used, a ground start button must be provided at each PFT set.
IMPORTANT: Only 2500MMGB, 2500MMGT, or 500MM sets may be used as PFT sets. Only loop-start and ground start trunks can be used for PFT service (no DID or tie trunks). Also, voice terminals that share a cable with an ADU may not be used as PFT sets.
If power fails (switch has lost power or a major fault has occurred), a contact closure is provided to the Central Office (CO) over a dedicated pair of wires. The CO then makes all DID trunks busy. When power is restored, the closure is removed and the CO restores DID service. External alarm contacts are provided on the front of the ETU for use as required.
Note: It is recommended that customers with DID service make provisions with their CO to provide this arrangement.
The ETUs are mounted on the cross-connect backboard. Connections are through 25-pair receptacle-ended (CO and SIP) and plug-ended (switch line and trunk) connectors. Modular jacks are provided for the -48 V control signal from the CPU/Memory and for additional ETUs. Screw terminals are provided for the connection of external alarms.
Figure 2-33shows a single-line voice terminal that has been connected as a Power Failure Transfer station. In normal operation, the CPU/Memory CP supplies -48 Vdc to the ETU. The voice terminal is connected through the ETU to the station port CP and can support all calling activities. The trunk connection through the ETU to the trunk port supports normal trunk calls.
