Amusing place for a visit, nice little adventure but worth the visit, wellies are necessary!
The communication bunker was known technically as a PR1 (protected repeater station, type 1), comprising a two-level bunker with heavy blast doors. It is semi-sunken, with the main distribution frame and active equipment on the ground floor and power plant and ventilation system in the basement below ground.
Repeater stations were locations where the signals on telephone cables were amplified to counteract the electrical losses that tend to make speech fainter. The majority of repeater stations were located at intermediate places between telephone exchanges. This one of the main trunk telephone (and television) cable routes, having a number of important circuits passing through it. It was constructed at a time when all repeaters (amplifiers) used thermionic valves (vacuum tubes), which required far more electrical power than the solid-state amplifiers of today. Accordingly the repeater station had a substantial power plant, with its own electricity substation, a large generator (removed some years ago) and storage batteries. The station had equipment stores, a test desk, repair workshop and eating/recreation facilities.