The Fixed Survey Meter or FSM introduced in 1958, could be operated from within the post with a cable leading to the detector mounted externally and protected by a polycarbonate dome.
The PDRM82 (F) was the fixed desktop version of the new Portable Dose Rate Meter, that were manufactured by Plessey and introduced during the 1980s, gave more accurate readings and used standard 'C' cell torch batteries that lasted many times longer, up to 400 hours of operation.