TBSK (Trait Block Shift Keying) modem is a low-speed, short-range audio wireless communication implementation.
You can try sending and receiving half-duplex texts on your PC or smartphone.
Prepare a computer and a smartphone or two or more smartphones. If a combination of a computer and a smartphone, it is easier the computer side is the transmitter.
Select the same tone format with the communication peer and press the start button.
In case of iPhone/iPad, after allowing audio access, tap the microphone icon in the address bar to stop/start the microphone for reset.