🡩
 Home
Telephones
A phone line tester for the hearing impaired
First posted May 1998
Last update Mar 15, 2015

This page was first begun on August 18, 1997 using Homesite 2.5. It was compleated on November 27, 1997 but was not actually posted until May 1998 when I got my first personal website. It was moved to this location on September 28, 2012, and updated using Homesite 5.5, 15 years later. Except for updateing some of the code, this section remains pertty much as it was when first written in 1997.

This is an easy to use, easy to make tester for deaf or severely hearing impaired persons which will allow them to detect telephone line current, dial tone, busy signals and that loud pulsating screech you get when the receiver is off the hook. The user can also detect when a voice or recording is on the line.

This device is easy to make for anyone who has experience with soldering small wires, and a bit of mechanical skill in jerry-rigging parts together. The complete device can be made from new parts for about $30 or $40, (1997 Radio Shack prices). If the builder is one of those people like me who tinkers with computer and electronic parts, and has lots of old components laying around, you may be able to build it for little or no cost.

This device is very useful for deaf persons who need to diagnose problems with TTY lines or computer modems.

How it works.

The cone of a small amplified loud speaker is exposed so the user can lightly place their finger on the speaker to detect its vibration. There is also a light or LED (light emitting diode), which will indicate whether a DC voltage is present on the phone line. Optional parts can allow the user to check for defective phone cords, and (depending on how comfortable they are in working on wires) even trouble shoot cables behind outlet plates and at the phone company's interface box.

How to use it.

After turning the unit on, the user rests a finger lightly on the speaker cone and plugs in the unit's phone cord into the suspect phone line. If there is a DC voltage present, the LED will light. If there is any sound on the line such as dial tone or voice, the user can detect that by the varied vibration of the speaker. I was surprised how easy it was for my friend that I made the first one for to detect the difference between the sounds created by the phone company, such as ringing and busy signals.