British Telecom Tester 301B - Page 1
Forum section: electronics / testgear

author: dexters_lab
author_rank: Unknown
timestamp: March 03, 2014, 11:17:56 pm
content: just something i picked up...a well used 'Tester 301B' cable fault locator that uses TDR (http://en.wikipedia.org/wiki/Time-domain_reflectometry)cant find much about these on the interwebs but it seems to date from about 1993.Operation looks pretty simple, basic oscilloscope type view to see the waveform reflected with a moveable cursor on the trace using a 10 turn pot which simply changes a LCD readout to the distance from the device. It appears it measures from 100 meters to about 2 kilometers.Came with an external psu for charging the internal ni-cd batteries (which are completely shot) so it's powered up with 12v from the bench psu.Internally it's not as complex as i thought it was going to be.I may do something more on my youtube channel if there is any interest?Would welcome suggestions of things to try with it? It has no value to me so i can do anything to it

author: SeanB
author_rank: Super Contributor
timestamp: March 04, 2014, 06:21:43 pm
content: I would pop a new battery pack in it and use it. I know enough people who would like to be able to easily isolate a cable fault on a network and would use it.

author: dexters_lab
author_rank: Unknown
timestamp: March 04, 2014, 09:19:24 pm
content: i could clean it up i guesstesting it might be an issue

author: atw60444
author_rank: Contributor
timestamp: March 04, 2014, 09:44:20 pm
content: Quote from: dexters_lab on March 04, 2014, 09:19:24 pmMake yourself a cable simulatorhttp://www.samhallas.co.uk/repository/documents/cable_simulator.pdfThey don't tend to trust the field technicians with test equipment that needs much skill nowadays. They are expected to use FastTest (voice response service into the line test system) and JDSU or EXFO hand held testers.Jon

author: dexters_lab
author_rank: Unknown
timestamp: March 04, 2014, 09:55:17 pm
content: perfect, i will try that out and see if it's working correctly

author: SeanB
author_rank: Super Contributor
timestamp: March 06, 2014, 04:12:46 am
content: Easier is you just take a full reel of cheap CAT5 cable and dig out the inside end, then simply join the 4 pairs in series. That way you have a 400m long cable, and can introduce opens or shorts at 5 points at defined lengths on it.

author: dexters_lab
author_rank: Unknown
timestamp: March 06, 2014, 11:35:05 am
content: hmm, i have a nearly full reel of STP Cat5 here i could try it withwould the STP shielding and it being in a coil affect the signal?

author: SeanB
author_rank: Super Contributor
timestamp: March 06, 2014, 08:42:22 pm
content: Not at all. Just use a pair and it will work fine. The beauty of twisted pair..... Being designed for phone cabling it will be a close match length wise on the meter reading.

author: dexters_lab
author_rank: Unknown
timestamp: May 02, 2014, 07:25:43 am
content: with thanks to those that have already commented i have done some tests with this using a part box of cat5will be cleaning this up and will make some new battery packs for it (eventually)

author: gteman
author_rank: Newbie
timestamp: April 09, 2017, 10:29:32 am
content: Wow haven't seen one off these in many a year. sorry for bumping an old post but I used to build these, the chances are I flow soldered this and possibly inspected it.It should have initials on the underneath of the board GW if it was me or JF if it was June that inspected it.edgcumbe instruments is now gone with a few blocks of flats replacing it thats progress for you.Graham

author: ralphrmartin
author_rank: Frequent Contributor
timestamp: April 09, 2017, 01:36:51 pm
content: Sell it as a useful device for people with lots of long part reels of cable to sell, who need to know how much is on the part reel? Although I suppose >100m for a part reel would have to be a pretty big reel...

author: dexters_lab
author_rank: Unknown
timestamp: April 09, 2017, 05:13:14 pm
content: Quote from: gteman on April 09, 2017, 10:29:32 amit's funny you used to make them, someone on youtube commented that they helped design the prototype!i sold it at a radio rally last year

author: gteman
author_rank: Newbie
timestamp: April 09, 2017, 06:09:17 pm
content: I watched your youtube video earlier and tried to comment but they just disappearedI do remember the front panel and case being designed at Edgcumbe Instruments when I was there.The battery pack in one off these was blame for a fire that burnt down the new end of the factory back in the late 80's

author: Cerebus
author_rank: Super Contributor
timestamp: April 10, 2017, 01:07:53 am
content: Quote from: atw60444 on March 04, 2014, 09:44:20 pmGiven my experiences they are probably right not to trust them - mind you, it's their own fault for not training them properly. I had a 'technician' out to fix a fault on my voice line a couple of years back. He asked me what I could hear on the line -me: "Just noise."him: "What kind of noise?"me: "Just white noise"him: blank lookme: "You know, white noise."him: blank lookme: "Gaussian noise?"him: blank lookme: "Fsssssssshhhhhhhhh?"Turns out that they are so poorly trained or educated nowadays that "white noise" is a phrase that not even sparks a vague memory of a training class half slept through. This despite "Signal to Noise Ratio" being one of their own official pass/fail criteria for a copper pair.

author: The Soulman
author_rank: Super Contributor
timestamp: April 10, 2017, 09:10:17 am
content: Quote from: gteman on April 09, 2017, 06:09:17 pmIf you have any information or documentation on this thing feel free to share it here.

author: gteman
author_rank: Newbie
timestamp: April 11, 2017, 07:54:49 pm
content: How about a picture of the production line post fire lol.A slighty younger me holding a 301B