Slashdot Mirror
Build Your Own Rotary-Dial Cell Phone
hwestiii writes "Yet another indicator of how unrepresentative of the main Slashdot crowd I am (meaning 'old') is that, like vinyl records, 8-track tapes, and Pintos, I can remember when rotary dial phones were items of everyday use, and not some object of retro-cool pseudo-nostalgia. Imagine my delight, then at finding this project in which an old rotary phone is turned into a cell phone. To give credit where its due, I originally found it linked from Hack A Day. I know nothing about home-built electronics projects, but this is enough to make me want to learn. If this catches on, imagine what they'll have to do to those 'turn off your cell phone' messages that play in movie theatres."
A quick trick of interest, perhaps good if you're ever in a situation where you can't use the dial pad and can't generate DTMF tones, is the super easy method of dialing a phone with nothing but the hangup switch.
On a mechanical phone (eg, any cheapo phone that doesn't need power or beep or anything), pick it up and listen for dialtone. Then just tap the hang-up switch with pauses for each number. For example, if calling 708-482-0623, you tap the switch 7 times, pause, then 10 times, pause, then 8 times, pause, etc. Rinse & repeat.
It's dirt simple, and most of us already know this, but... it's an easy fun thing to know.
How come you say "dial" a number instead of push a number?
Anyone *really* old remember the letter prefix phone numbers? "Just call Zenith 4265. Operators standing by..."Insert witty comment *here*. I'm fresh out of wit...
Many years ago, probably the late 80's, I was at a restaurant in Vancouver waiting for a friend who appeared to be late. I was directed to the restaurant courtesy phone and was miffed when I discovered that the call from the restaurant to his home was long distance (Vancouver had some weird long distance rules back then, now fixed). Anyway, the courtesy phone had a long distance restrictor device attached so I pulsed dialed manually by clicking the receiver. All my tapping caused some curious looks from people in the restaurant waiting area, but it worked.
I believe digital switches are much less tolerant and "manual" rotary dialing will no longer work now on digital circuits.
Not at home, but I have one in my office at work. I found it in a cabinet and it was like finding gold; I had not seen or used one since I was about 8.
I took it into my office and put it on the secondary line. I also love the sound of its mechanical ringer when calls come in, and the comments I get when people see it there.
They're amazed when I tell them that yes, it works, and yes you can still dial with it on today's phone system.
Unfortunately, when the analog line it's on is replaced by a VG248 "fake analog" line, which is really VoIP with an adapter, the rotary dial pulses will no longer work. {:(
An era of backwards compatibility is slowly ending. Pulse dialing will slowly stop working on analog phone lines over the next few years or so...
-Z
I find this to be an interesting comment, because non-rotary phones are *NOT* digital. They (well, in North America) are DTMF, meaning they work with two tones played at once to signal the button press. This is all calculated by having one frequency for each row, and another for each column. When you press a button, the row and column tones are played, making the indicated dual tone. As such, you cannot dial a DTMF phone by whistling, unless you are capable of whistling two notes at the same time.
One other interesting bit of trivia is that DTMF phones can have a fourth column of buttons A, B, C, and D. However, these typically would only be found on test sets and AUTOVON (US Military) phone systems.