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A digital audio transmitter is quite a complicated device to build, especially in a small space and it would also require a power source and in-depth knowledge of the internal circuitry of the laptop to be able to interface to it.
Just as a check, can you confirm the laptop doesn't have Bluetooth, if it has, try turning it off, the settings are probably in the control panel somewhere but not under the audio devices category. The other possible, but unlikely source is an SPDIF interface if the laptop has one. Some have a dedicated SPDIF socket, some hide it behind the headphone jack socket. If you look closely down the headphone socket hole in a dark room you would see a dim red light if it has one behind it.
Brian.
When I disable the audio device in the control panel those "digital" signals are also stopped.
Trying to get VHF signal down a phone line designed to handle no more than a few KHz woud be very difficult to do and very difficult to hide.
As we have explained many times, if you can't see a high gain directional antenna (think *BIG* TV antenna) or a large dish pointing at you, with nothing obstructing the line of sight, the chances of the signals being picked up are negligible.
I'm not sure which one you are referring to. Please tell me the post number it is in so I can take a look.So are you saying that the antenna I showed is not suitable to detect RF from the telephone?
Yes, VHF can pass through a capacitor but the next parts in line are the rectifiers, they will not let it through.
Without the AC ringing voltage on the line, no voltages beyond the capcitor exist and the whole ringer circuit, the IC and piezo included have no power source.
The problem would be that the 6V AC would have to be present before ANY voltage reached the ringer so to provide it power to work from it would need to be more than 6V.
I know audio frequencies cannot get pass the capacitor. At what minimum frequency does it start to pass the capacitor?
How about learning some real electronics and give up on these paranoid delusions
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