TEW4980 is designed to be used either as a transmit or a receive transformer in the ISDN primary access network, interfacing SIEMENS PEB2235 and PEB2236 to a 75, 100 or 120 ohm line.
When in transmit mode, connect the two primary windings in parallel, pin 1 to 3 and pin 2 to 4.
When in receive mode, connect the two primary windings in series, pin 2 to pin 3, thus forming a center tap at pin 2/3.

Typical applications are:
• Primary rate ISDN network nodes.
• PBX or computer to T1/CEPT Digital trunks.
• TDM Multiplexers.