Line isolation transformer
Safety device for telephones
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.
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.
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This article is adapted from the Wikipedia article “Line isolation transformer”, written by its contributors and licensed under CC BY-SA 4.0. Fathomly has changed the layout, removed citation markers, navigation and maintenance notices, and adjusted punctuation. This adapted version is shared under the same license. For references, see the original article.
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