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Old 3rd Jun 2019, 8:18 pm   #3
Join Date: Aug 2009
Location: Worthing, Sussex, UK.
Posts: 512
Default Re: GPO planset with external extensions

Some versions of planset use a transistor to detect the extension being off hook rather than a relay. This makes it polarity sensitive.

Also external extensions use need an earth to work ringing the main.
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