Me, deep in the night, reading about modem signals and off the hook. I love forum threads. They have taught me more than I can imagine.
Exactly this. It’s called a “hook” and when the phone is “off the hook” that’s the thing it is off of. Being off the hook means the phone is powered up and connected to the local loop. When the phone is “on hook” that means it is disconnected from the loop and awaiting the pulsed ring signal.
Desk phones have a reversible hook so that it keeps the button depressed when the phone is in the cradle but doesn’t catch when you attempt to pick it up.
On modem signals in the old days, the + was equivalent to “flashing” the hook, or quickly disconnecting and reconnecting to the loop, and the AT command H1 told the modem to go “on hook” while H0 told it to go “off hook”.
Back before the DTMF network, when everyone used pulse modulated phones, the “pulses” were caused by going in and off hook in a specific pattern. You could actually make a phone call from a rotary payphone by flashing the hook in the pattern that mimicked the rotary dial pulsing the line as it rotated back to home position.
In the really old days, the hand crank served much the same purpose, but actually supplied electricity to the local loop; when the phone was on hook (which was a big metal thing the earpiece sat in) someone else turning the crank would make all the phones on the loop ring; you picked up if the ring matched the number of rings for your extension.
mwalimu@baraza.africa 6 months ago
SgtAStrawberry@lemmy.world 6 months ago
So that’s how you used the old hand crank phones, I never know. I thought you turned the crank to get power into the phone and then told the person working the switch bord who you want is to talk to. And that when you were telling you sometimes needed to re turn the crank to get more power.
hperrin@lemmy.world 6 months ago
Yes! Another phone nerd!
One small clarification. There’s not really anything special to the pulses for pulse dialing. One pulse for the number 1, all the way to nine pulses for number 9, and then ten pulses for a number 0.
froh42@lemmy.world 6 months ago
In the 80s there was a way to cheat phone booths in Germany: With a small tool that had an adjustment screw you could position the hook switch to an exact position where the phone booth had already connected the line but did not yet power up the rest of the machinery (including coin counters)
You could then call arbitrary nunbers by pulse dialing using the hook switch (the rotary dial was still powered down)
Basically a EU pulse dial version of phreaking.
My father, who died this year, used this a lot too make “free” calls.