The main LF/VLF receiver in the Fleet from late WW2 years right up to the introduction of the CJK receiver in the mid 1950's, and thereafter served with the Fleet to the end of our story [1980 and beyond] as a stop-gap to plug a break in reception.  This was caused by the ICS receivers [CJD and CJA] not having an overlap between the CJD's upper maximum frequency and the CJA's lowest useable frequency. The break in reception was between 525kHz and 2.01 MHz approximately. Between them, the B41 and its sister receiver, the B40 covered this gap. They were only supplanted when the FTA solved the problem of giving continuous coverage from VLF to HF.

Fitted widely throughout  the Fleet perhaps more than any other piece of kit !

Click here B41.pdf for a description, and here B41C.pdf for a picture.