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KENT  BR5 3KP   Tel. Orpington  32121
Cray Avenue
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email - Gerald Clode
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Induction loop is a term historically used to describe an electromagnetic communication system , which exploits a phenomenon that was (according to anecdote) first noticed accidentally, on a battlefield during World War 1 . A telegraph linesman was running tests on a field telephone cable loop, when a radio operator, within the loop, noticed sounds in a headphone that had a faulty, short-circuited, jack-plug. The original explanation of the phenomenon was by way of conventional transformer theory. Mr Barry Pyatt, Senior Equipment Engineer and Project Leader at Rediffusion-Reditune (Rediffusion House, Cray Avenue, Orpington, Kent) in 1973 mathematically demonstrated that the phenomenon would vary according to an installation's global geographical location.
Complex computer simulations were run at a London university, taking account the magnitude and dip angle of the earth’s magnetic field, and these gave weight to Pyatt’s assertion that the phenomenon was rather more due to a modulation of the earths magnetic field, rather than simple transformer coupling theory. Rediffusion was, at that time, a multi-national organisation, and tests conducted by the company's South African and American operations also indicated that Pyatt's predictions were measurably correct. Rediffusion-Reditune were granted a "Ministry of Posts & Telecommunications Licence" and developed one of the first commercial induction loop amplifiers (product code LAA 100) for use in the industrial world for communication in noisy environments. Hearing protection hardware and telecoil assemblies for the system came from A & M Hearing Aids in Crawley, West Sussex.
The required adherence to the maximum average ampere/turn criteria laid down by MINPOSTEL was achieved by indirectly heated thermocouple technology. Companies who produce products like this can be found on the internet The whole gamut of the history, technology and Rediffusion's development of induction loop systems was internally published in an
aide-mémoire for the (then) global Rediffusion / British Electric Traction empire, and distributed amongst an international contingent of engineers and company directors attending an engineering conference at the Bromley Court Hotel, 1974. Mr Pyatt became Group Leader of engineering development at Rediffusion-Reditune, and his team went on to develop a four band VNB VLF (120kHz) frequency modulated system.

Barry Pyatt    Group Leader, (Special Systems Engineering Development)
Barry Pyatt worked for Rediffusion  Reditune between 1973 and 1976 in the position of:  Group Leader, (Special Systems Engineering Development) and I headed a small team of engineers involved in the development of magnetic wave communication systems, and also a system which pre-empted Spectral Recording. This was an important field for Reditune, who were always struggling to get more and more music onto their proprietory endless-loop tape cassettes.

Barry's main contribution
to Reditune was in the design and development of the LAA100/LR2 induction loop system.
Below is an outline of the Induction Loop system as featured on Wikipedia.  

Below are pages from the Reditune brochures outlining the technical specifications of the Ear Defender product.
Barry Pyatt ( Centre )  with P.Stanley (L) and A. Barr (R)

Barry Pyatt ( Centre ) with P.Stanley (L) and A.Barr (R)

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Barry would be very interest to strike up contact with Arthur Barr or John Childs, if anyone knows their whereabouts.