This requires the generation of tones. This is generally followed by a 2400Hz tone for the same time. Signalling is a two way thing, so each burst is replied to with an acknowledgement. Now you can place a call. Start of pulsing, indicates whether a national or international call is being placed.
Timings can vary quite dramatically.
Right voicemail may be the bane of a lot of peoples lives, but for the phreak it is a joy. A voicemail system is a glorified ansafone with enough fun things to play with to keep you occupied. Now here it starts to get a bit repetitive because you need to sequentially dial a few hundred numbers to glean a good set of voicemail systems. A voicemail system will either tell you it is the voicemail system of company X or it will just prompt you for a mailbox number and password. Not all systems are up 24hrs a day, and it is nice to find one that is.