TV Licensing Detector Vans

The TV Licence detector vans were first introduced in 1946, I suspect they used the German radio frequency detection method as at the time the homes had few electrical devices in the home.  

These vans detected no more than the frequency of an electrical device in the home and has the TV sets were CRT tubes with a small screen like the one below.

The equipment the TV licensing unit used possibly only detected that a signal was being transmitted and didn't know if it was from a TV set or a radio, prior to 1971 you also needed a licence to listen to the radio, not just a TV that in 1946 only had one channel. 

There is a video on You Tube about a person who bought an old TVL detector van and they refurbished it and a TV show, The One Show, broadcast it been used to detect a signal from a TV. They had to use an old TV, a portable, and connect it to a battery on a driveway, to get a signal from the set but it didn't show any channel that the set was on as as it couldn't detect anything but a radio frequency. 

As soon as TV's went to other methods for a TV set the detector vans became defunct, surplus to requirements, and have been ever since the CRT tubes were not used in TV's. 

TVL, now run by Capita since July 2002, renew their vans when the older ones need replacing. One or two people have seem inside the modern vans and claim there is nothing inside them, they are just a van with the TV Licensing logo on them and nothing else. Even TVL won't tell the Ministry of Defence how their detection equipment works, which to me suggests that they do not have the equipment that detects anything more than a radio detection device that was used by Germany in WW2.   

This is just a personal bit about myself and TV's. In October 2016 I had a bill from my electric and gas supplier and it stated that my Smart meter had used around £27 on TV usage, the problem was I only had the TV on around 5 times, approximately, in the times the bill, yearly usage, stated and that was to use a games console, any other TV usage would have been related to the PC's monitor, that I used constantly throughout the day. Even a utility company couldn't say I watched the TV that much as the set was off most of the time. Utility companies, if they can detect a devices signature from it being on they cannot detect the difference between a PC monitor and a TV set with a tuner! I cancelled my licence in August 2016 after just 5 years of paying for a licence.