monline

I guess this feature is available on most mobile phones, but I only know it for sure for Nokia phones. When entering a number (eg. in your phonebook), you can add short pauses or explicit waits to the dialing sequence (to separate the phone number from the extension number).

While in your dialing mode (or phone number editing mode), press the asterisk key ("*") three times to get a "p" (stands for "pause") or four times to get a "w" (stands for "wait"). The "p" means that the phone waits a few seconds during the dial before sending over the remaining numbers. The "w" means that the phone sends over everything before the "w" and then asks for confirmation (once the call is picked up on the other end) to send over the remaining part.

Eg. if you type a phone number as +3612345678p104, then it will dial +3612345678, waits a few seconds and dials 104. You can put in more pauses (several "p"s) to increase the pause duration in case the receiving PBX at the other end requires it.

Using the other variant (+3612345678w104) means it'll dial +3612345678, waits for the call to be picked up, then shows a confirmation on the screen for sending 104. On my Nokia N95 the text of the confirmation is: "send DTMF?"

P.S.: the extra numbers (eg. extension number) you send over after a connection is estabilished are called DTMF (aka. touch) tones. Nokia has a FAQ entry on how to use DTMF tones.

P.S.2: some PBXes (private telephone systems) require special rules for various DTMF tones. Eg. I've read that some systems require a "*" tone between two adjacent and identical numbers. Ie. a DTMF code like 1007 would require you to type "10*07" in your mobile. Some PBXes require a hash ("#") at the end of DTMF tones.