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Daimler LQ3-20 Burovox communication system

Beat Weibel
Posts: 185
Joined: Sat Feb 27, 2016 4:13 pm
Location: Munich

Daimler LQ3-20 Burovox communication system

Post by Beat Weibel »

Hello experts

This is maybe a bit an unusual question:
My Daimler LQ 3-20 has a Burovox communication system between the passenger compartment and the driver. Reviewing the attached US patent, I think I know how it should work and how it should be wired. However I fail to open the bakelite microphone to check the connections. Any idea how to open it?

Best regards and thanks for every hint
Beat
Here is a picture of the loudspeaker in the driver's compartment:
used-1935-daimler-lq3~20-limousine-145-1417464-54-640.jpg
Attachments
US1838586A_Original_document_20200405113253 Burovox Telephone System.pdf
(656.25 KiB) Downloaded 66 times

Soundmike
Posts: 76
Joined: Thu Mar 17, 2016 8:54 am

Re: Daimler LQ3-20 Burovox communication system

Post by Soundmike »

Hi Beat. The cover on the microphone has a left hand thread, it will unscrew to reveal a carbon type microphone capsule. Do not attempt to dismantle as the carbon granules will be lost! The microphone and speaker work on the same principal as the old manual telephone. The sound vibration of the mic diaphragm cause compression of the carbon granules varying its resistance. This is in series with the battery and high impedance speaker. The system is not very sensitive, you will probably need to speak very close to the mic! The carbon in the microphone tend to "pack down", give it a series of sharp knocks to restore operation! The speaker can be checked by connecting a 1.5 volt cell across it. It should click when connected/disconnected. I have got mine to work but the horn is missing off the speaker. Might need to flog one off a trumpet!
Regards, Mike.

Beat Weibel
Posts: 185
Joined: Sat Feb 27, 2016 4:13 pm
Location: Munich

Re: Daimler LQ3-20 Burovox communication system

Post by Beat Weibel »

Hello Mike
The left-hand thread seems to be the key! I probably tried to open the the wrong way.
Will not touch the capsule....
Thanks for your help and kind regards
Beat

Simon Hyslop

Re: Daimler LQ3-20 Burovox communication system

Post by Simon Hyslop »

I was very interested to read about the carbon granules. I seem to remember, although my wife says she's never seen it, people in older films sometimes hitting or tapping the microphone end of a phone if the connection seemed poor. Presumably this continued in a similar way to the practice of tapping an aneroid barometer when the reason had disappeared once it had supplanted the mercury barometer. Another useful useless piece of information I'm now pleased to know about.

Vortex O'Plinth
Extra-Wise Man
Extra-Wise Man
Posts: 1065
Joined: Fri Feb 12, 2016 8:15 pm
Location: Gloucestershire

Re: Daimler LQ3-20 Burovox communication system

Post by Vortex O'Plinth »

Simon Hyslop wrote: Mon Apr 06, 2020 10:31 am .........Presumably this continued in a similar way to the practice of tapping an aneroid barometer when the reason had disappeared once it had supplanted the mercury barometer. Another useful useless piece of information I'm now pleased to know about.
To go off topic for a moment, both mercury and aneroid barometers respond to a light tap Simon. Both have 'stiction' in the connection between the pressure sensing element and the dial needle. This combats the very small forces and displacements that record the change in pressure. In addition tapping a mercury barometer allows the formation of a proper meniscus of the mercury inside the tube for a correct reading. Tapping my (aneroid) barometer is part of my daily ritual - on the trip between my first cup of coffee and the loo... :D
Nick

"Don't bother with the Air & Space Museum - there's nothing to see.......".

Soundmike
Posts: 76
Joined: Thu Mar 17, 2016 8:54 am

Re: Daimler LQ3-20 Burovox communication system

Post by Soundmike »

A simple upgrade would be to install a modern Peizo or dynamic mic capsule and small amplifier module. It would improve the sensitivity and audio quality considerably, but it wouldn't be original would it!!!!

ron.rsp
Posts: 118
Joined: Sat Feb 20, 2016 9:42 am

Re: Daimler LQ3-20 Burovox communication system

Post by ron.rsp »

Beat, Do you have a pic of the microphone end of the system, I have the same set-up but the microphone is long gone!

Ron

Beat Weibel
Posts: 185
Joined: Sat Feb 27, 2016 4:13 pm
Location: Munich

Re: Daimler LQ3-20 Burovox communication system

Post by Beat Weibel »

Hi Ron
Here is a first picture. I will send better and closer ones as soon as possible.
Best regards
Beat
9813694.jpg

ron.rsp
Posts: 118
Joined: Sat Feb 20, 2016 9:42 am

Re: Daimler LQ3-20 Burovox communication system

Post by ron.rsp »

Thank you Beat, much appreciated.

Ron.

Beat Weibel
Posts: 185
Joined: Sat Feb 27, 2016 4:13 pm
Location: Munich

Re: Daimler LQ3-20 Burovox communication system

Post by Beat Weibel »

Hi Ron and all
Here is a better picture.
Unfortunately, the microphone doesn't work. However, the trumpet seems to work.
I will check the internet for miniature microphone and amplifier.
Best wishes
Beat
Burovox Microphone.jpg

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