Technical and Research Processes RK-2

From Baird Television Website

"There was also a ‘BBC-Marconi’ condenser, designed by Henry Joseph Round in 1934 and manufactured in small numbers in London by Technical & Research Processes Ltd. (Visatone)."

H J Round was a prolific inventor and engineer, who filed 117 patents, with his last coming at the age of 82. His output ranged from microphones to echolocation to power stations!

We have also been informed that T&RP was a part of the Marconi outfit. Post- war they made some condenser mics for Decca. They had a strong HF resonance which was useful for Decca's early FFRR (full frequency range recording), which began in 1944.  It seems likely that our microphones are some of these later microphones for Decca

This is a very early and very rare valve condenser microphone. It was possibly made for Decca. It has a small diameter capsule that screws directly onto the grid terminal on the top of the A1065 vacuum tube. The microphone had a separate battery power supply which also contained some of the circuit and an output transformer, which gave a balanced low impedance signal and could drive cable over long distances.

Sadly our examples have long been separated from their power supplies.

Thanks to Roger Beardsley for providing additional information.

A 1934 BBC-Marconi Tech­nical and Research Processes Ltd. studio valve condenser microphone, at the Coutant Website