#30 Line in use for visual or other type of alerts.

[Al]

Line in use for visual or other type of alerts.
I would like to hook a light (using relay and Raspi GPIO) to know when the phone line is in use.
I dont know if NCID could detect when the line is in use or is more a hadware issue.

[Ed Attfield]

The POTS (plain old telephone service) phone line in North America, with all phones on-hook, measures about 48 volts DC.
It's a current source, so the off-hook voltage varies depending on your phone equipment, but will be something below 10 volts. I measured my wife's call today at 7.5 volts.
When the phone rings you will get somewhere around 90 volts AC. Try not to be holding the wires when the phone rings, or in a thunderstorm.

For a simple visual indicator, you can build something like this.
http://www.bowdenshobbycircuits.info/page12.htm#inuse.gif

I had something like it on my phone when I was on a party line, but I couldn't find a circuit diagram for it. Mine ran off a nine volt battery and I think it only had one transistor.

You want high value resistors on the input, and you want to run it off batteries for isolation.

[BTodCox]

To add to Ed's comments, most modems do not report line in use, so NCID will not generally know when a phone is off-hook.

Here's as commercially available solution Viking Indicator

[Ed Attfield]

In recent reading of documentation for the Connexant modem, I found a feature that might give us indication of another phone going off hook on the line.

I was hoping to use it to stop the outgoing hangup message so I didn't have to shout over it to answer a legitimate call from an 800 number.

[John L. Chmielewski]

Sounds good.

On Thu, Jul 29, 2021 at 02:59:13PM -0000, Ed Attfield wrote:

In recent reading of documentation for the Connexant modem, I found a feature that might give us indication of another phone going off hook on the line.

I was hoping to use it to stop the outgoing hangup message so I didn't have to shout over it to answer a legitimate call from an 800 number.

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[feature-requests:#30] Line in use for visual or other type of alerts.

Status: closed
Group: Next_Release_(example)
Labels: Line in use
Created: Thu Jun 25, 2020 03:41 AM UTC by Al
Last Updated: Thu Jul 29, 2021 01:15 PM UTC
Owner: Ed Attfield

Line in use for visual or other type of alerts.
I would like to hook a light (using relay and Raspi GPIO) to know when the phone line is in use.
I dont know if NCID could detect when the line is in use or is more a hadware issue.

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John