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Old 5th Jan 2020, 1:30 pm   #1
dagskarlsen
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Default Transistorised transmitter capsules.

Here are some, but when and where should I use the different versions?
The first one works in field telephones with 3V battery, and so does the black one in the next row of pictures, The other ones works in CB telephones where all the dc goes trough the transmitter. Hard to compare, I do not know how to measure or systemize.
They will not work if to much current is "stolen" in the anti sidetone bridge.
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Last edited by dagskarlsen; 5th Jan 2020 at 1:37 pm. Reason: Adding text
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Old 5th Jan 2020, 1:31 pm   #2
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Default Re: Transitorazed transmitter capsules

Here are some more:
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Last edited by dagskarlsen; 5th Jan 2020 at 1:33 pm. Reason: Problems with pictures.
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Old 5th Jan 2020, 11:26 pm   #3
Graham G3ZVT
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Default Re: Transistorised transmitter capsules.

I use the homemade configuration that "ThePillenwerfer" posted about HERE
Just treak the 100K to get the desired sensitivity.

Works fine on a GPO232 on a BT line and various PABXs

Also I have found the zeners to be unnecessary, just complete the bridge with ordinary diodes.
As usual with these simple circuits, I don't bother with a custom PCB, I just use a fragment of project board.
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Last edited by Graham G3ZVT; 5th Jan 2020 at 11:35 pm.
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Old 6th Jan 2020, 11:38 am   #4
ThePillenwerfer
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Default Re: Transistorised transmitter capsules.

Thanks, Rambo. Glad it's of use.

As for the zeners I'm inclined to agree. They are only to offer a bit of protection to the transistor as if you answer while the 'phone is actually ringing it's exposed to the ringing current for a fraction of a second. You can bet that if I hadn't included them somebody would say I should have and they add minuscule cost and no bulk. If fact, if you could be sure that the polarity would never be reversed, you could do without the diodes altogether.
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