Editing Telephony Application Programming Interface (section)

==Telephone address format==
TAPI uses Microsoft canonical address format for telephone numbers<ref name="MSDN_TAPI_Canonical_Address">{{cite web| url = https://msdn.microsoft.com/en-us/library/ms726017.aspx#canonical_addresses| title = MSDN: TAPI Applications - Device Control - Canonical Address| date = 7 January 2021}}</ref><ref name="TechNet_Canonical_Address">{{cite web| url = https://technet.microsoft.com/ru-ru/library/cc772545(v=ws.10).aspx| title = Microsoft Technet: Dialing Rules and Canonical Address Format| date = 2 July 2012}}</ref> to make phone calls. It is a derivative of [[E.123]] international notation.

The canonical address is a text string with the following format: <code>+Country&#9251;(AreaCode)&#9251; SubscriberNumber | Subaddress ^ Name CRLF</code>. Area code, subaddress and name are optional; the latter can carry extension number for [[direct inward dialing]] and [[caller ID|calling party name]], as used by [[ISDN]]/[[E-carrier|E1]]/[[T-carrier|T1]] telecommunication protocols.

Dialing rules are used to transform the canonical phone number into a dialable calling sequence for the [[modem]], depending on the user's location. The dialing rules include variable-length dialing for area code, trunk access and international access prefixes, as well as central office access and [[Telephone card|calling card]]/[[credit card]] numbers.<ref name="MSDN_TAPI_Canonical_Address"/><ref name="TechNet_Canonical_Address"/> 

The calling sequence can contain dialable numbers such as digits <code>0-9</code> and [[DTMF]] tones <code>ABCD*#</code>, formatting characters <code> ␣ . -</code>, and control characters <code>!  P T , W @ $ ? ;</code> which correspond to the Dial command of the Hayes [[AT command set]]. The following control characters are defined: <ref name="MSDN_TAPI_Canonical_Address"/>

:! - hookflash, i.e. half second [[on-hook]] followed by half second [[off-hook]];
:P - [[pulse dialing]] mode;
:T - [[tone dialing]] mode;
:, - pause dialing (duration specified by the device);
:W - wait for [[dial tone]];
:@ - wait for "quiet answer", i.e. the [[ringback tone]] followed by several seconds of silence;
:$ - wait for a billing signal, such as credit card prompt tone;
:? - indicates that the user is to be prompted before continuing (results in an application error since the API has no means to implement a user prompt);
:<nowiki>;</nowiki>  - the number is not complete and will be finished later (only valid in a dialable number).