SFERICS
Technical details

The antennas were two 272 turn crossed loop aerials tuned to 10kc/s with a separate sense antenna. each of the loop aerials was enclosed in a fibre-board case about 3 feet square and about five inches deep. They were installed in an outdoor cabinet about thirty feet from the building. The aerials were tuned from the front panel of the console in which they fed the four stages of a push-pull amplifier. This was all valve technology of the early nineteen fifties era.

The display was a centrally mounted CRT with a compass rose for the operator to determine the direction of each 'flash'. The console included a test oscillator that was switched in to align each stage of the amplifiers.