[gh02t]

Back in the days of phone line modems, there used to be a program that you could type in a number, the modem would emit the corresponding tones, and then you could pick up a phone and it'd already be connected. I can't remember what the one I saw was, but I'm sure there were multiple different ones, and I also vaguely recall there were dedicated physical machines that could before that.

[neckro23]

You could do this with any terminal program. Your modem won't emit any noise until it hears a carrier tone, so you could just dial, pick up the extension, hang up the modem.