Where can I buy the pocket telegraph in "Chongqing spy war"

I remember when the physics teacher in high school was talking about radio waves, she took one of those things.

In fact, that thing uses long and short tones as signals, which is pre-coded.

For example, one long note and three short notes are you.

Two short notes, two long notes.-Okay,

Then, I sent a message, received it and found the corresponding word.

It's almost the same as the current computer binary, but it's coded with 0 and 1

I guess you don't really want it. You should be able to buy it from the manufacturer that provides experimental instruments. Why use text messages when you have them?