The Phone Device
A phone device is a device that supports the phone device class and that
includes some or all of the following elements:
- Hookswitch/transducer. This is a means for audio input and output. The Telephony API recognizes
that a phone device can have several transducers, which can be activated and
deactivated (taken offhook or placed onhook) under application or manual user
control. TAPI identifies three types of hookswitch devices common to many phone sets:
Handset The traditional mouth-and-ear piece combination that must be manually lifted
from a cradle and held against the user's ear.
Speakerphone Enables the user to conduct calls hands-free. The hookswitch state of a
speakerphone can usually be changed both manually and by the API. The speakerphone
can be internal or external to the phone device. The speaker part of a
speakerphone allows multiple listeners.
Headset Enables the user to conduct calls hands-free. The hookswitch state of a
headset can usually be changed both manually and by the API.
A hookswitch must be offhook to allow audio data to be sent to and/or received
by the corresponding transducer.
- Volume Control/Gain Control/Mute. Each hookswitch device is the pairing of a speaker and a microphone
component. The API provides for volume control and muting of speaker components and for
gain control or muting of microphone components.
- Ringer. A means for alerting users, usually through a bell. A phone device can be
able to ring in a variety of modes or patterns.
- Display. A mechanism for visually presenting messages to the user. A phone display is
characterized by its number of rows and columns.
- Phone buttons. An array of buttons. Whenever the user presses a button on the phone set,
the API reports that the corresponding button was pressed. Button-lamp IDs
identify a button and lamp pair. Of course, it is possible to have button-lamp pairs
with either no button or no lamp. Button-lamp IDs are integer values that range
from 0 to the maximum number of button-lamps available on the phone device,
minus one. Each button belongs to a button class. Classes include call appearance
buttons, feature buttons, keypad buttons, and local buttons.
- Lamps. An array of lamps (such as LEDs) individually controllable from the API.
Lamps can be lit in different modes by varying the on and off frequency. The
button-lamp ID identifies the lamp.
- Data areas. Memory areas in the phone device where instruction code or data can be
downloaded to and/or uploaded from. The downloaded information would affect the
behavior (or in other words, program) the phone device.
TAPI allows an application to monitor and control elements of the phone
device. The most useful elements for an application are the hookswitch devices. The
phone set can act as an audio I/O device (to the computer) with volume control,
gain control and mute, a ringer (for alerting the user), data areas (for
programming the phone), and perhaps a display, though the computer's display is more
capable. The application writer is discouraged from directly controlling or
using phone lamps or phone buttons, because lamp and button capabilities can vary
widely among phone sets, and applications can quickly become tailored to
specific phone sets.
There is no guaranteed core set of services supported by all phone devices as
there is for line devices (the Basic Telephony Services). Therefore, before an
application can use a phone device, the application must first determine the
exact capabilities of the phone device. Telephony capability varies with the
configuration (client versus client/server), the telephone hardware, and the
service-provider software. Applications should make no assumptions as to what
telephony capabilities are available. An application determines the device
capabilities of a phone device by calling the
phoneGetDevCaps function. A phone's device capabilities indicate which of these elements
exist for each phone device present in the system and what their capabilities are.
Although strongly oriented toward real-life telephone sets, this abstraction
can provide a meaningful implementation (or subset thereof) for other devices as
well. Take as an example a separate headset directly connected and controllable
from the computer and operated as a phone device. Hookswitch changes can be
triggered by detection of voice energy (offhook) or a period of silence (onhook);
ringing can be emulated by the generation of an audible signal into the
headset; a display can be emulated through text-to-speech conversion.
A phone device need not be realized in hardware, but can instead be emulated
in software using a mouse- or keyboard-driven graphical command interface and
the computer's speaker or sound system. Such a "soft phone" can be an application
that uses TAPI. It can also be a service provider, which can be listed as a
phone device available to other applications through the API, and as such is
assigned a phone device ID.
Depending on the environment and configuration, phone sets can be shared
devices between the application and the switch. Some minor provision is made in the
API where the switch can temporarily suspend the API's control of a phone
device.
- Software for developers
-
Delphi Components
.Net Components
Software for Android Developers
- More information resources
-
MegaDetailed.Net
Unix Manual Pages
Delphi Examples
- Databases for Amazon shops developers
-
Amazon Categories Database
Browse Nodes Database
