Telephone question

easy, do you want the 'full-blown-solution [schematic] for a way to either prevent picking up a line in use, or a way to notify a line in use also?

Nothing fancy, just allow the phone to answer the one that is ringing. ...Jim Thompson

automatic, or need to know which line?

Automagical... whichever line rings (first), picking up phone answers the first one that was ringing. ...Jim Thompson

Radio Shack used to sell such a device. IIRC it's basically a latching relay with the coil(s) activated by the ringing current.

Dunno if they or anyone else still markets something like this... I bought ours back in the late 1980s.

Or, you could get a DPDT switch and install it near the phone.

Jon

Then it wouldn't ring unless it was in the right position

something like a dual coil latching relay triggered by the ring voltage might work

-Lasse

Search for "2-line switch".

These guys in Taiwan have one that looks to meet your request, and apparently they'll ship.

Best regards, Spehro Pefhany

Yes, but then you can only pick up the line that rung last time, you have no choice. Maybe that doesn't matter.

Jon

And, I have an 8-line PBX in my house. We have intercom, ringing at all phones, and can select which line to call out on by pressing a button. Very much overkill, but we wanted the intercom feature, and have a business and home line. It was bought used, made by NEC for the US market, and has been running for almost 25 years in its second life. I'm waiting for the thing to die so I can upgrade, but it WON'T die!

Jon

Thanks, Spehro, Looks perfect! ...Jim Thompson

I have, in storage, a commercially produced telephone accessory [cost about $50] to enable a single line telephone to operate two telco lines. Although the device could sit in view showing which line Ring indicators, 'line in use' indicators, AND HOLD indicators multi color LEDs; it could be placed out of sight because it had no buttons. You operated transitions by using ON HOOK/OFF HOOK, or 'flash' button on the keyboard. Very handy to place a present conversation on HOLD in order to answer the other line's incoming call. Plus, if the other person terminated the call while on HOLD; the unit sensed the hang up and released the line.

it

also?

ringing.

Sounds straight forward; a couple of ring detectors, driving a latching relay.

?-)

The ring signal is a strong (I think the specification is 96V p-p) 20Hz AC signal on top of the 48V DC to the phone. It's got enough oomph behind it to ring real, physical bells in several phones at once (or in my case, one honkin' big bell that can be heard all over my 5 acres when the shop door is open).

When you pick up the phone, about 48V/1200ohms flows through the phone, providing power to the phone and a signal to the central office that the phone is picked up.

Surely you can figure it out from there?