Line isolation transformer
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A line isolation transformer for telephone use is a special type of impedance matching transformer that is used to couple telephone land lines to subscriber equipment to prevent dangerous common mode voltages from appearing on the line. It has a specific 600Ω input impedance which matches the telephone equipment.[1]
A "wet" type will maintain its characteristics while passing the DC current needed to seize the telephone line (signal off-hook to the central office). It is also made with a gapped magnetic core that is not used in normal transformers. A "dry" isolation transformer need not carry DC current and an alternative DC path would be provided.[2]
See also
[edit]References
[edit]- ^ Sound & Communications. Sound & Communications Publications. 1987.
- ^ AN-5 TRANSFORMER-BASED PHONE LINE INTERFACES (DAA, FXO) by Joe Randolph, retrieved 2018 March 20