Logo audio in

If you need a very easy circuit, then you can try following test:

1. Use the output of a loudspeaker to have enough level
2. Use a diode or a bridge rectifier to get d.c. voltage
3. Connect to an analog input of the Logo controller
4. Check with a test program, e.g. an analog threshold trigger, if the level is okay to differ between normal operating of microfon level and PTT
5. if level is okay, then the output of threshold trigger is usable for counting up 5 times (see example from Ella_68

If you want to detect special signals, then describe them in details. Maybe it's also possible to generate a tone e.g. 1kHz. Then use an amplifier like example from Ella_68, but don't use a relay.
A square wave with enough level for a fast counter input can be used with a digital threshold trigger.

Regards, Scorp

Hello Scorp,

In my opinion, this is a daring circuit. On the one hand, the impedance of the speaker output must match the circuit (if the impedance is too low, the output stage will burn out). On the other hand, you don't know the peak-to-peak voltage at the speaker output (could be too high for the logo). In addition, one does not know how the output stage of the radio receiver works. If it runs in push-pull mode (loudspeakers between two output stage transistors), the device will definitely be destroyed.

!! At the price that an aeronautical radio system costs, I would strongly advise against building such a circuit !!

greeting, Ella_68

You are right with the higher risk for the receiver. I see no problem with impedance and voltage. I also would check the signal, before i connect it to the Logo controller, but the best way is a higher quality circuit.

Depend on the location of the creator he can buy a ready module at an electronic distributor. Maybe a sound activated electrical switch (clapper) is good enough to detect the signal.

Alternatively to the loudspeaker output it is possible, that the receiver has a line output ? There are different ways possible, but not without knowing all details.

Regards, Scorp

Many thanks to all. I solved the problem with a Audio Relay:

https://www.rdlnet.com/product.php?page=130

[snip]

Many thanks and best regards,