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General Vintage Technology Discussions For general discussions about vintage radio and other vintage electronics etc. |
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10th Apr 2018, 1:23 pm | #1 |
Heptode
Join Date: Oct 2006
Location: Leeds, West Yorkshire, UK.
Posts: 598
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VHF/UHF radio and telephone voice switch systems
By the above, I mean the network of headsets/microphones, frequency selectors, transmitters and receivers and phone lines, such as those used in Emergency Services control rooms, Coastguard and Air Traffic Control towers.
Does anyone know if the operator's voice, via the headset/handset microphone, is connected directly to the radio/phone or does it go through some sort of processing first ? In most cases noise-cancelling microphones are used which takes care of ambient clutter but I wondered if any other adjustments or enhancements are made such as bass, treble and amplification ? I know the previous vintage system used at Leeds Bradford Airport used a device called a VOGAD to ensure a constant output from the controller's microphone. Thankyou. |
10th Apr 2018, 3:56 pm | #2 |
Moderator
Join Date: Mar 2012
Location: Fife, Scotland, UK.
Posts: 22,902
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Re: VHF/UHF radio and telephone voice switch systems
Voice Operated Gain Adjusting Device.
Just a straight gain compressor. Redifon did their own with long strings of diodes as variable resistors (GK203 manual) Plessey did some VOGAD devices in their SL600 radio IC family. (The Hitch-Hiker's Guide to the Galaxy has this to say about Vogads.....) David
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10th Apr 2018, 4:18 pm | #3 |
Dekatron
Join Date: Feb 2005
Location: West Cumbria (CA13), UK
Posts: 6,130
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Re: VHF/UHF radio and telephone voice switch systems
Perhaps it should have been "Voice Operated Gain Obliterating Noise" then.
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10th Apr 2018, 4:49 pm | #4 |
Heptode
Join Date: Oct 2006
Location: Leeds, West Yorkshire, UK.
Posts: 598
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Re: VHF/UHF radio and telephone voice switch systems
Back in the day, the Leeds Bradford controllers used headsets with NC magnetic microphones, as opposed to moving coil or electret types. Plug one of these into a normal cassette recorder for a test and the output is very clear, if a little quiet, and quite treble-heavy. However, when connected via a matching in-line amplifier, the result is noticeably superior. Maybe the VOGAD performed this same function.
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