Vox Radio Microphone, 1961-1966
Detail from the JMI dealer's catalogue of 1964.
The Vox Radio Microphone in its initial form was the work of Alan Harding, who had joined Jennings in 1960 from Colben Radio in Crayford. Colben was one of the companies that assisted Jennings in the production of its organs, though its main drive was naturally radios.
Work on the system, which was fully transistorised (both transmitter and receiver), began in late 1961 / early 1962, the impetus doubtless being the draft proposal for radio mics issued by the General Post Office, the body responsible for regulating and licencing wireless telecommunications.
In preparation, Tom registered a trade name with the Patent Office. The Vox Radio Microphone was to have been called the Vox "Transair", though the name was evidently dropped along the way.
Trade Mark number 826638.
During the lead-up to the Russell Hotel Trade Fair of August 1962, JMI signalled:
Preview of the Russell Hotel Fair, August 1962. A page on the Fair can be found here.
No name given, simply a "development". As it turned out, the system took some time to bring to market, the first adverts appearing in early 1964. Alan Harding remembers the challenges posed by the GPO specification documents of November 1962 and July 1963: systems to operate at 175Mc/s (an extremely high frequency), to dissipate no more than 10mW, and to be incapable of generating interference in other applications. It should be said though that Jennings was not the only company at work in the field. Lustraphone, a long-established microphone manufacturer based in Lowestoft, had evidenly run several leagues ahead, four of its systems gaining GPO licences by the end of l963 (two transistorised, two valve based). At least one BBC outside broadcast was produced in late 1962 with its "Radiomic".
In terms of GPO approval, licencing by July 1963 had been divided into two categories: (1) general "Public Address"; and (2) Film and Stage. JMI will probably have applied for both.
February 1964, business trade journal. The journal also printed a copy of the promotional image at the head of this page.
Quite how Alan's work intersected with that of Lustraphone is unknown. The "Association of Public Address Engineers", for its part, took a strong line in promoting the Lustraphone systems, publishing in its journal a detailed overview of the company's work in the month - March 1964 - that Jennings was scheduled to demonstrate its radio mic at the Public Address Trade Fair. Coincidence? Nothing was said of JMI's demonstration. The APAE does not seem to have liked Jennings all that much.
4th and 5th March 1964, the demonstration of the Radio Mic at the Public Address Trade Fair, the first attended by JMI as a member of the Association.
As for other excursions, Alan Harding remembers taking an early version of the JMI unit to Pinewood Studios, where a James Bond was being filmed at the time - much interest, but no orders. And he also recalled demonstrating the system in a large Catholic church in London (for the celebrant at mass). Rodney Angell, who worked as an assistant to the JMI Research and Design Department, remembered attempts to build the transmitter into guitars.
Detail from the JMI pricelist printed in February 1964.
"Type C" narrow-band equipment allowed several channels to be operated simultaneously, each with its own transmitter and frequency. The specifications were set out for licence applicants in a number of documents drawn up by the GPO.
June 1964. Lustraphone had received official approval (from the GPO) for its narrow band multi-channel receivers in September and December 1963.
At present the only known circuit diagram for the first versions of the Vox Radio Microphones is OS/052, undated, but probably early 1964.
JMI circuit diagram OS/052. OS/053, for the AC50 mark 2, has an initial creation date of April 1964.
It should be possible to illustrate a surviving unit from 1964 shortly. The microphone conventionally supplied with the system was a Shure Commando, available also from JMI as a separate item.
Late 1964, redesign
Image from a test report on the Vox Radio Microphone published in January 1965.
Redesign of the unit (as illustrated in the picture above) was clearly well underway by late August 1964, when the radio mic was shown at the Russell Hotel Trade Fair:
Small detail from a shot taken at the Russell Hotel Trade Fair, late August 1964.
Detail from the JMI pricelist printed in September 1964.
Shortly after the prices above had been printed, Tom Jennings set out his view of the Radio Mic. for JMI dealers:
"Vox Sound Equipment Limited" PA brochure, late 1964.
Thanks to Martin, a picture of a superb Vox Radio Microphone set, probably early 1965.
The new circuits, designed in collaboration with Burndept Electronics, one of JMI's principal sub-contractors, were formalised in December 1964 and early 1965. Four diagrams resulted.
These were: OS/069 for the receiver unit, drawn on 28/12/64; OS/070 for the transmitter unit, drawn on 21/12/64; OS/078A and OS/078B, special requirements, introduced in March 1965.
Competition, 1965
Just to illustrate for the time being, a few of the competing systems that had come to market by 1965 - boom times.
Mid 1965, the Reslo systems, the general scheme much as JMI's in terms of the specifications mentioned. The JMI squelch circuit was expressed in circuit diagram OS/78B.
Late 1965, advert for the Wolec system, externally very familiar somehow, marketed by SNS of Bournemouth. SNS later made amps used by Slade.
Back to the page on the ribbon and dynamic microphones offered by Vox, 1960-1968.
Back to the main index page on Vox Public Address equipment.