The applications that demand high bandwidths and fast switching speeds Telecom transformers are utilized. It is used to isolates the signal between primary and secondary windings. There are several types of telecom transformers normally used. Few of transformer options include DSL , xDSL , E1 , T1 , ISDN , LAN , WAN & ATM transformer models. A lot of Modern transformers are also available. A DSL or xDSL transformer uses the digital subscriber loop (DSL) or extended digital subscribe loop (xDSL) for telecommunication protocols (Broadband). A T1 or E1 type of transformer is designed to use along with a T1 line or an E1 line. An ISDN type of transformer is the usual telecommunications transformer used for integrated tele-services digital network (ISDN), ISDN is an international standard for the digital transmission of voice and data. A LAN type of transformer is designed for use in a local area network (LAN), while a WAN type is used in a wide area network (WAN). An ATM type of transformer works with asynchronous transfer mode (ATM).

Performance specifications for any telecom transformers include the range of operating frequency, direct current resistance, insertion loss, high potential (hipot) level, 3-decibel (dB) bandwidth, operating temperature, and maximum dimension.

Direct current resistance or commonly known as DCR is the resistance of the telecom transformer’s winding as measured with DC current. It is commonly specified as a maximum rating. Insertion loss is the measured loss through the device excluding the power division factor. It is measured in dB and calculated as the ratio of output power to input power. HIPOT level is the maximum voltage a telecom transformer can take without breaking the winding. 3 dB bandwidth is the frequency range.

Telecom transformers usually differ in terms of package type and method of packing. Integrated circuit (IC) package types include flat pack, single in-line package, dual in-line package, and small outline integrated circuit.

Board-level telecom transformers can employ either surface mounted technology or through hole technology. SMT adds components to a PCB by soldering component leads on to the top surface of the board. Through-hole technology fixes the components by inserting leads through holes and then soldering the leads in place on the other side of the board.