NEC Electra Elite 48/192 COIB(4)-U10 ETU 4 Circuit CO Interface Unit with CID (Refurbished)NEC Electra Elite 48 192 COIB(4) U10 ETU The Central Office Caller ID ETU detects Caller ID signals from the central office and sends caller indentification to the CPUB() U10 ETU and supports four outside (CO PBX) lines. More Information: Mnfr. Part #: 750445 Only works with Caller ID lines Supports four outside (CO PBX) lines For use with the NEC Electra Elite 48 192 phone system.