Author Topic: Polarity By-Pass... key...  (Read 132 times)

Offline Babybearjs

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Polarity By-Pass... key...
« on: December 26, 2019, 03:33:26 AM »
has anyone ever tried to add a key switch to a touch tone phone to "Lock" it out so its a answer only phone. using a key to change the polarity.
John

Offline dsk

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Re: Polarity By-Pass... key...
« Reply #1 on: December 26, 2019, 04:33:17 AM »
Not tested, but would it not be enough to short F and RR to block the dial?  Makes it easier to ad a simple switch. (with key)
dsk

Offline Babybearjs

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Re: Polarity By-Pass... key...
« Reply #2 on: December 26, 2019, 08:52:38 AM »
on a rotary dial that would work, as for a touch tone... would polarity reversal work? I know I had to reverse the wiring on my 2702 to get it to dial out... (Grn-Red to Red-Grn)
John

Offline dsk

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Re: Polarity By-Pass... key...
« Reply #3 on: December 26, 2019, 09:47:36 AM »
Right! newer touch tone sets are not depending on polarity.  For WE 500 to 2500 with polarity sensitive dial pads the polarity change will block the phone from dialing with the pad.  Yes! to change polarity you need a more complex switch than what you need to short F and RR.

Looking at the schematics for the 2500dm on the TCI library, it is enough to short F and RR.  If you want to have the blocking external from the phone, the polarity switch is an easy solution. You may use a 4-way wall switch  :)

Offline Key2871

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Re: Polarity By-Pass... key...
« Reply #4 on: December 26, 2019, 12:48:03 PM »
Polarity reversal would be sufficient, but just pulling a wire so it can't dial out plus just as effective. You could actually set the phones keys to select a particular line key to close the open on the dial so you can dial out.
Versus having a set that just can't dial out.
KEN