Das Telephone Line Tester (Wilcom Model T303B)

Yesterday at the MIT flea I happened upon this gem, a little bad boy from Wilcom called the “MODEL T303B SIGNALING SENDER.” What is it do you ask? I have no idea. What does it do? It beeps. How much did I pay for it? $7.

Wilcom Line Tester
Wilcom Line Tester

It’s dated 03/1983 Manufacture and appears to have been owned by GE. Here’s what I’ve been able to figure out. It’s a solid looking 10x7x7 inch box with two handles. It also has two hinges and a missing latch where a lid went at one time. On the face, it includes two lovely chrome handles and six quarter inch jacks, most of which are balanced. It includes an array of no less than 23 beautiful square push buttons. It has a rotary selector with two decimal digits labeled “SEND LEVEL (-dBm).” Along the base run 8 “one at a time” 1980s buttons. It includes one push/pull switch to turn it on, as well as a toggle switch. Lastly, a speaker and volume knob are located on the upper right of the panel. I’ve been able to get it to send signal out of one of it’s jacks.

Upon dis-assembly I’ve discovered a solid looking 1980s pcb and IC arrangement. It includes a rechargeable battery and an internal transformer for charging (classy).

Now, functionally it’s pretty interesting. Upon power up, it lights several lamps. There are three buttons labeled DTMF, MF, and DP. While Dual Tone Multi Frequency dialing is commonplace, and many can remember Dial Pulse rotary phones, this also has support for Multi Frequency dialing, which I thought was cool. This phone also has 4 additional DTMF/MF numbers, A B C and D (Autovon style).

After power up, clicking the DTMF panel has no effect, however the device stores them into memory. Pressing SEND will fire off the previously entered DTMF sequence. Selecting MF generates unrecognizeable tones and DP clicks appropriately in the appropriate sequence. There is a way to store number sequences (not that I could tell you) and recalling any unused number generates a funky techno beat.

Unfortunately the majority of this seems to be geared toward testing trunk lines. It supports E/M lines, possibly in 2 and 4 wire arrangements. Unfortunately I don’t think I’ll ever be able to test this functionality. It appears that it will connect to a regular phone line (with a 1/4 inch to modular jack adapter). I have unfortunately been unable to figure out the necessary connections as of yet. Any help would be appreciated in the comments section. It has headset ports, generically and unhelpfully unlabeled as to which is speaker or mic (or both?) :(. There is also one button that is labeled ST3P which I have yet to identify.

You can select the level of the DTMF transmission in -dBm with the retro selector. A pair of green buttons is labeled “ON HK” and “OFF HK” which appear to mean on and off hook.

The coolest feature though is the “geek magnet” factor. Nobody at the flea (or the office) has been able to walk by without poking it. It’s pretty cool. The manual is available on eBay for $40 (which is…almost 6 times more than I paid for the box itself).


One thought on “Das Telephone Line Tester (Wilcom Model T303B)”

  1. I got one of these yesterday and have hooked it up successfully. It is great to use with project MF (http://www.projectmf.org/). In mine the batteries had died and I had to disconnect the batteries and hook up a large capacitor (820 uF, 25 V) in place of the batteries to properly filter the power supply. A regular 2-wire dial PSTN line can be connected to the 2W send jack and the switch put in 2W loop position. It uses a telco 310 plug. If you plug in a switchboard headset (type 52 or 53) to the headset jacks, you can have the coolest phone ever. I have a copy of the manual I will scan and post it to the http://www.telephonecollectors.org/ website. Contact me if you have questions.

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