DRICO

D Stock still retain the built-in emergency tunnel telephones (which discharge the current).

The DRICO equipment (which didn't discharge the current) was where the Connect radio handset is now located. Although it was retained at refurb, most of the doors were jammed shut. The timetabled booked stops were removed some while ago now.

DRICO equipment was fitted to trains, the wooden box, as you say, was the emergency tunnel telephone.

All tube tunnels still have the copper wires you asked about and all are operational. The DRICO is no longer used but all stocks carry a handset that clips onto the wires and switches off traction current. Contact with the Line Controller is then possible.

For those that like "dates" (as I do ;D ), I have the following dates that DRICO was commissioned:

09.03.52 - Northern Line
31.01.54 - Bakerloo Line
01.09.54 - Central Line
05.02.56 - Piccadilly Line
18.03.56 - Northern City Line
13.01.57 - Tunnel sections of the District Line for R and Q Stock trains only but excluding South Acton branch, East Putney – Southfields tunnel and between High Street Kensington and Edgware Road.
02.03.59 - Met, Circle and East London (which then included High Street - Edgware Road).
06.12.65 "Portable" Drico provided for Eastern Region drivers working goods trains over the East London Line.

Yes DRICO (DRIver-COntroller) was still in use when I began my LT career in 1977 although I didn't have much to do with it until 1979 when I transferred from Signals to the Telephone Section. Train radio did indeed replace DRICO but it took a while and I wouldn't mind betting there is still some DRICO kit around even though it hasn't been used for at least 20 years and was mostly removed by 1990.

Basically DRICO was a system superimposed over the tunnel telephone circuit tapped off the tunnel wire pair at each 'reset end' substation via isolating capacitors and DRICO test points were located at some station headwalls also tapped off the tunnel wires via a pair of capacitors into a TDB (track disconnection box). This box would be painted green with a red stripe painted horizontally across the lid and is where we (telephone linemen) would connect the DRICO test box which was basically a large hand held loudspeaker unit.

The DRICO handset did not trip the tunnel telephone circuit but connected to the Line Controller via a DRICO amplifier at the substation. The DRICO amplifiers were removed in the late 1980s IIRC. I don't know when the onboard train kit was removed but that was a job no doubt for the depot train techs. I can say that the Picc and District Line Controller DRICO equipment was alive and well at Earls Court until I removed the old telephone rack and four DRICO relay sets in 2004, the desk equipment had long gone but the wiring was extant until I had a tidy up to make way for all the new kit that was proposed for the Picc Controller.

I can also say that I found DRICO test points still connected to the tunnel wires at Holloway Road in the course of my regular tunnel telephone maintenance duties.

I never had any dealings with carrier wave when it was working though I was trained to maintain it. It was replaced by a train radio system then different to the Storno radio systems in used on the other lines. I installed the trial Victoria line train radio system line amplifiers and leaky feeder cabling in the Northern line tunnels between Tooting Bec and Colliers Wood circa 1988/9. It used fourteen Texscan amplifiers on separate transmit and receive leaky feeder cables in each tunnel with the main control equipment located at Tooting broadway. IIRC when installed on the Victoria line following the successfull field trial it was a cut down version using a single leaky feeder and amplifier chain per tunnel as both Tx and Rx following the convention of the Storno system in use on the other lines.

However, I did finally get to work on the carrier wave, I got the job of the final recovery of tunnel mounted trackside equipment once the train radio was operational. The last units were marshalled at Northumberland Park depot following recovery and then we hijacked some space on a P-Way train on a weekend possession to get them away for scrapping/reuse. I'm sure the kit went for scrap but the cases were mostly the double width Westinghouse equipment cases as used throughout the Victoria line so I expect they were refurbished by SOS.

I was once asked by the controller on the Northern line to do a DRICO test at South Wimbledon. I opened the box and the wires and speaker were filthy. So I just sat there for a couple of minutes, then called him up on the radio and said I had tried but got no reply. Test failed without even getting my hands dirty ;D

Used to be a b*gger to test in depots,you had to clip the DRICO leads of two trains together and see if you could talk to each other,used to be leads everywhere!!