[toast0]

The time required for a good hangup might vary a little bit from exchange to exchange. I recall occasionally being able to transfer to different handsets hanging up one before picking up the other. But not to the extent reported in some anecdotes where one end can hold the call open indefinitely.

[jjnoakes]

This is definitely true. I remember being able to quickly press and release the hangup button on a single phone and if I was quick enough the other person would remain on the line. I don't recall exactly where the threshold was, but I believe it was around a half a second or so.

[ThinkingGuy]

I remember being able to hang up the phone in one room, run to the next room, and pick up the phone and continue the conversation. My friends and I did this on several occasions. This was in the Atlanta area, in the late 1980s.

[eep_social]

Rapidly pressing and releasing the hang up button simulates pulse (as opposed to tone) dialing used by rotary phones.