How does 'W' work?
 

I think this question is most appropriate in the international section.

I don't recall any GSM phones that do not have 'P' pause & 'W' wait as possible 'numbers' to dial. I was going to ask how one used the 'W" but I played with the phone and this is how it worked.

What I learned. For example, in the USA PlatinumTel GSM requires you dial 835 to make international calls [didn't know that, did you!] a recording answers and than you dail the numbers you want without a '*', but with a '#' at the end.

To make things easier, I added the number to the address book and put two 'p's pauses in to automate the call.
835PP44792xxxxxxx#
Each pause is about 5 seconds. It works.
How does W= wait work? 835W44792xxxxxxx#
After the 835 is dialed it says press send to send.
So you manually release the wait. I have never seen this explained before.

Is this how it works on all phones?

Not sure there is a section for this.
All phones I know of. There was something similar on USR modems except that "W" waited for another dial tone. When the phone sees the "P" or "W" it shifts to DTMF dialing.

I don't know if this works for all but that's how it works with Nokia. Adding a w requires that you hit the talk key then the string you have specified will be toned out. P pauses for five seconds.