On Jun 21, 6:05*pm, "Arfa Daily" wrote:
wrote in message

...

Ok, I set up a 2p2t switch that turns off my in-home lines and instead
goes to an
RJ11 jack. The telco says I should test this to see if the problem is mine
or
theirs. SO far this is SOP.

So then me thinks, why should I have to scramble for a tel set to make a
test? *Why not just put an LED *there? So I need a 2700 ohn resistor in
series with the LED. I can still plug in the tel set, but the LED will
tell
me immediately what is going on as soon as I swich from whole-house to
test-circuit.

* * - = -

You would still need to watch out for the AC ringtone, as this will try to
stick a huge reverse voltage across your LED on every half cycle. Your
resistor can be much higher than 2.7k with modern high efficiency LEDs. I
think I would go for around 10k as the series resistor, and also put a
1N4007 diode in inverse parallel with the LED. Of course, this only all
works at all, if your telephone operator doesn't use line polarity reversal
for line status signalling. It's been a lot of years since I learnt all this
stuff at college, but I seem to recall that this used to be the case - at
least here in the UK anyway - and was the reason that there was a bridge
rectifier in the telephone, so that the polarity inside remained the same,
irrespective of what was going on polarity-wise on the line. Perhaps Robert
would be more current on that.

Arfa

Here in the US the telco sometimes would also do line reversal AFTER
you acquired the connection! Translates to Touch Tone Dialer didn't
work anymore! I haven't heard of it happening lately, but moot point,
every phone I've seen simply bridge rectifies and is done with it.