John T
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- Oct 15, 2005
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Thought I would post the most basic/simplistic bit of gear I worked on.
It was a Film Recorder that I serviced until I left the RAF in 1967. From the title sounds complex, but no.
A single valve (sorry if you don't know what a valve is you don't belong here.O-Ha) audio amplifier, the oputput fed to a old style GPO earphone, consisting of an electromagnet and a metal diaphram. Brazed into the centre of the diaphram was a gramaphone needle. Fixed to the earphone was a nut. The nut was mounted on a threaded bolt. About a 3 foot loop of 30mm film was tensioned arround a pulley system. The gramaphone needle was started on the outer edge of the film, a motor then drove the the film and bolt, the needle thus scribed a very long path round and across the film. Any sound was transferred to the film via the gramaphone needle as a scratch of varying depth. As you may imagine one very low quality playback was your lot.
This was used to record radio conversations between Air Traffic Control and aircraft, the idea being if there was an accident there was a record to refer to.
Playback was a case of simply switching the input of the audio amplifier to the earphone and a pair of headphones to the output. So simple, but in those days the way of getting a very long recording. If you hear no more from me you may assume that I am incarcerated for breech of the official secrets act. ({})
It was a Film Recorder that I serviced until I left the RAF in 1967. From the title sounds complex, but no.
A single valve (sorry if you don't know what a valve is you don't belong here.O-Ha) audio amplifier, the oputput fed to a old style GPO earphone, consisting of an electromagnet and a metal diaphram. Brazed into the centre of the diaphram was a gramaphone needle. Fixed to the earphone was a nut. The nut was mounted on a threaded bolt. About a 3 foot loop of 30mm film was tensioned arround a pulley system. The gramaphone needle was started on the outer edge of the film, a motor then drove the the film and bolt, the needle thus scribed a very long path round and across the film. Any sound was transferred to the film via the gramaphone needle as a scratch of varying depth. As you may imagine one very low quality playback was your lot.
This was used to record radio conversations between Air Traffic Control and aircraft, the idea being if there was an accident there was a record to refer to.
Playback was a case of simply switching the input of the audio amplifier to the earphone and a pair of headphones to the output. So simple, but in those days the way of getting a very long recording. If you hear no more from me you may assume that I am incarcerated for breech of the official secrets act. ({})