The Old Joel on Software Forum: Part 4 (of 5) - Why do we have # and * on phones?

Why do we have # and * on phones?

I know that we have uses for them these days what with phone menus and *69 and all but I recall in the days of my youth, when a lot of phones were still dial phones, wondering why they put those two extra keys on those new touch tone phone pads.

Does anyone know the history on this? Did they anticipate phone menus and special services in the future? Was it just to make the pad rectangular? Was it so the president could launch a nuclear attack from a pay phone?

name withheld out of cowardice
Thursday, February 12, 2004

There are four more buttons there, too (ABCD), you just can't see them :-)

Each column corresponded to one tone; each row had another. Pressing a button sent two tones, one for the column and one for the row. There was a 4x4 scheme but consumer phones only had 3x4 of the buttons actually installed.

Joel Spolsky
Fog Creek Software
Thursday, February 12, 2004

From http://www.phonewarehouse.com/thedial.htm

...

Bell Labs developed DTMF in order to have a phone dialing system that could travel across microwave links and work rapidly with computer controlled phone exchanges. Each transmitted digit consists of two separate audio tones that are mixed together (see fig.3). The four vertical columns on the phone keypad are known as the high group and the four horizontal rows as the low group; the digit 8 is composed of 1336 Hz and 852 Hz. The level of each tone is within 3 dB of the other, (the telephone company calls this "Twist"). A complete touch-tone phone pad has 16 digits, as opposed to ten on a pulse phone dial. Besides the numerals 0 to 9, a DTMF "dial" has *, #, A, B, C, and D. Although the letters are not normally found on consumer phones, the IC in the phone is capable of generating them.

The * sign is usually called "star" or "asterisk." The # sign, often referred to as the "pound sign." is actually called an octothorpe. Although many phone users have never used these digits - they are not, after all, ordinarily used in dialing phone numbers - they are used for control purposes, phone answering machines, bringing up remote bases, electronic banking, and repeater control. The one use of the octothorpe that may be familiar occurs in dialing international phone calls from phones in the United States. After dialing the complete phone number, dialing the octothorpe lets the phone exchange know you've finished dialing. It can now begin routing your phone call; without the octothorpe, it would wait and "time out" before switching your call.

m
Thursday, February 12, 2004

Thanks. Sometimes this forum is better than Google for geek stuff.

name withheld out of cowardice
Thursday, February 12, 2004

Agree. I guess the number of knowledgable people browing this forum is huge and these days I try to put a quesiton on JoS along with my search on Google! :)

JD
http://www.phpkid.org

JD
Thursday, February 12, 2004

I use # and * to search the telephone directory online using regular expressions. Really. You should try is some time.

Rob VH
Thursday, February 12, 2004

The '#' sign origins and some other interesting info @

http://www.word-detective.com/072999.html

Code Monkey
Thursday, February 12, 2004

"A complete touch-tone phone pad has 16 digits, as opposed to ten on a pulse phone dial. Besides the numerals 0 to 9, a DTMF "dial" has *, #, A, B, C, and D. "

What were those guys thinking? Everybody knows that counting up to 16, the digits are 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, A, B, C, D, E, and F

Tom H
Thursday, February 12, 2004

Thanks code monkey- that's even better and answers my original question.

name withheld out of cowardice
Thursday, February 12, 2004

and why does a phone have numbers going from top left to bottom right (1 to 9) when a calculator has those same numbers going from bottom left to top right??

Tapiwa
Thursday, February 12, 2004

I've previously asked my father, who was at Bell Labs during the Touch Tone invention era, about the number layout question. He says that they did usability studies for whether the numbers should be arranged like a calculator or like they are currently.

Keep in mind that in the late 60's and early 70's there were very FEW people using "calculators", or more likely mechanical adding machines with paper tape.

The Public had a much easier time seeing the numbers arranged in increasing order as it ended up.

Dave Torok
Thursday, February 12, 2004

To add to the above, the * sign is usually used by the PBX (or equipment over at the Central Office to which your home is connected) to activate a feature, while # is used to cancel it. For instance, France Telecom over here uses *21*0123456789 to route all calls made to this phone to the number 0123456789, while #21# is used to cancel rerouting.

But then, few people are confortable with the way phones are designed today, even with advanced technical degrees (been there, seen that.) Does Fisher Price make phones? :-)

FredF
Thursday, February 12, 2004

A bit off topic, but since someone brought up Fisher-Price...

My mother recently mailed me a old-style telephone pull toy for my 18 month baby. (example below). She tracked it down via ebay so that her grandson could have the same one I had as a kid. I thought it was a little strange; he's never seen a dial phone, and only rarely a desk phone as everyone around him uses cell or cordless. And he doesn't quite have the coordination to dial. But he loves to pull it around.

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=3175571977&category=2528

Will
Thursday, February 12, 2004

FYI in Australia and Britain we call the '#' key the hash key.

Matthew Lock
Thursday, February 12, 2004

...producing the enjoyable result that some less-attentive people call C# "C hash"

[grin]

Philo

Philo
Thursday, February 12, 2004

"less-attentive"? I've always done it because I was attentive ;-)

Some things, C# and the sound of nails scraping a blackboard with them, just don't sound good!

i like i
Friday, February 13, 2004

# is also called the "jail" key. :)

Friday, February 13, 2004

"A bit off topic, but since someone brought up Fisher-Price..."

I used to have one of those! :)

Kyralessa
Friday, February 13, 2004

The same government agency that forced American families to give all kids the Fisher-Price chatter phone also issued one copy of Fleetwood Mac's "Rumours" to every household in every suburb in 1976...

Conspiracy Theorist
Friday, February 13, 2004