Please help with suitable tester

[remtel]

Please could someone suggest other than an analogue multi-meter, a suitable tester out there, that can be used to test for an analogue phone connected at the end of a cable pair from the MDF/IDF. The old fashioned and tedious way is to use an analogue multi-meter across the pair, then when reversing the polarity, you will see a kick in the meter indicating a connected analogue phone. The kick being the capacitor charging/discharging. I have heard of a little selfmade tester with an LED that does the sdame thing with a krone plug, which is so much easier. Does anybody have one of these that they would like to sell on, or have a copy of the circuit diagram. Thankyou !