TAPIEx ActiveX Control v3.6


Dialable Addresses

The dialable address format is the form in which an address is passed to a service provider that handles telephone numbers. The following details concern dialable addresses on a phone network.

The dialable number format allows multiple destination addresses to be supplied at once. This ability can be useful if the service provider offers some form of inverse multiplexing by setting up calls to each of the specified destinations and then managing the information stream as a single high-bandwidth media stream. The application perceives this group of calls as a single call because it receives only a single call handle representing the aggregate of the individual phone calls.

It is also possible to support inverse multiplexing at the application level. To do this, the application would set up a series of individual calls and synchronize their media streams.

Subaddressing is a capability provided on ISDN lines that allows more information than just a single telephone number to be used when dialing. This additional information can specify an individual telephone extension to ring or, in a computing environment, a particular application to be alerted. Other parameters can describe the required aspects of a requested connection, such as rate and timing.

If subaddressing is supported by a service provider, the application includes this in the address passed to any operation that requires one.

A dialable phone address contains part addressing information and is part navigational in nature. Any input string that does not begin with a "+" character is presumed not to be in canonical format and therefore to be in dialable address format, and is returned to the application unmodified. A dialable address is a text string with the following structure:

DialableNumber | Subaddress ^ Name CRLF ...

The components of this structure are given in the following table.

Component Meaning
DialableNumber Digits and modifiers 0-9 A-D * # , ! W w P p T t @ $ ? ; delimited by | ^ CRLF or the end of the dialable address string. The plus sign (+) is a valid character in dialable strings. It indicates that the phone number is a fully-qualified international number.

Within the DialableNumber, note the following definitions:

0-9 A-D * #

Characters corresponding to the DTMF and/or pulse digits.

! Hex (21). Indicates that a hookflash (one-half second onhook, followed by one-half second offhook before continuing) is to be inserted in the dial string.
P p Hex (50) or Hex (70). Indicates that pulse dialing is to be used for the digits following it.
T t Hex (54) or Hex (74). Indicates that tone (DTMF) dialing is to be used for the digits following it.
, Hex (27). Indicates that dialing is to be paused. The duration of a pause is device specific and can be retrieved from the line's device capabilities. Multiple commas can be used to provide longer pauses.
W w Hex (57) or Hex (77). An uppercase or lowercase W indicates that dialing should proceed only after a dial tone has been detected.
@ Hex (40). Indicates that dialing is to "wait for quiet answer" before dialing the remainder of the dialable address. This means to wait for at least one ringback tone followed by several seconds of silence.
$ Hex (24). Indicates that dialing the billing information is to wait for a "billing signal" (such as a credit card prompt tone).
? Hex (3F). Indicates that the user is to be prompted before continuing with dialing. The provider does not actually do the prompting, but the presence of the "?" forces the provider to reject the string as invalid, alerting the application to the need to break it into pieces and prompt the user in-between.
; Hex (3B). If placed at the end of a partially specified dialable address string, it indicates that the dialable number information is incomplete and more address information will be provided later. The ";" component is only allowed in the DialableNumber portion of an address.
| Hex (7C), and is optional. If present, the information following it up to the next + | ^ CRLF, or the end of the dialable address string is treated as subaddress information (as for an ISDN subaddress).
Subaddress A variably sized string containing a subaddress. The string is delimited by the next + | ^ CRLF or the end of the address string. When dialing, subaddress information is passed to the remote party. It can be for an ISDN subaddress, an e-mail address, and so on.
^ Hex (5E), and is optional. If present, the information following it up to the next CRLF or the end of the dialable address string is treated as an ISDN name.
Name A variably sized string treated as name information. Name is delimited by CRLF or the end of the dialable address string. When dialing, name information is passed to the remote party.
CRLF Hex (0D) followed by Hex (0A). If present, this optional character indicates that another dialable number is following this one. It is used to separate multiple dialable addresses as part of a single address string (for inverse multiplexing).

Address translation can be used to translate an address from canonical format to dialable format.