sorry if you all have answered this a million times before ...

whats the difference between long and short
does it matter what it is set to?

One day with all the help on here I will be an expert mobile phone user ......... (as always)

Two nuggets I dug up from Google.

Short for Dual Tone Multi-Frequency, the system used by touch-tone telephones. DTMF assigns a specific frequency, or tone, to each key so that it can easily be identified by a microprocessor.

DTMF means Dual Tone Modulation Frequency. This systems is intended to transmit keys pressed on a keyboard through an audio channel such as a telephone line or a radio connection. For each pressed key two audio frequencies are emitted: one (higher) corresponds to the column in which the key is in, and the other (lower) corresponds to the row. This encoding handles a maximum of 4 rows and 4 columns, that means 16 keys (from 0 to 9, *, #, and from A to D). The lower frequency (corresponding to the row) is emitted with less amplitude than the higher one, and precisely of 2 dB (that means that the amplitude is 1.259 times smaller).

A pat on the back for anyone who can tell us all what CCITT-5 stands for, without using Google. :P

of the top of my head, CCITT is a signalling system, but as for anymore details, I'm not sure, and would have to go to google for information.

DTMF is, in simplemans' terms, touch-tone rather than pulse dialling. The DTMF long/short option on your mobile is most likely useless and either will work fine

I couldn't even begin to attempt to know what CCITT is, without using Google.

[To quote a little funny. Yesterday, I couldn't spell engineer. Now I are one.]

Sorry, misread the question - feel free to delete this post.

The difference between long and short is just the length of the tone for each key press, I have yet to see the need for long or short option... must be some reason?