The Analog Display Services Interface, normally abbreviated to ADSI, is a Bell Communications Research (Bellcore) standard that defines a protocol for data transmission over a voice-grade telephony channel. Devices such as a central office or interactive voice response (IVR) system that can generate ADSI data can communicate with ADSI compatible telephones. These telephones have some processing capability, an area of read and write memory, a display screen, navigation keys (to scroll information up, down, left and right), and softkeys. The softkeys can be programmed to perform different functions at different times.
ADSI uses a technique by which the telephone channel is taken over for the transmission of modem-encoded data, during which time the handset is muted to minimize annoyance to the telephone user. A stream of commands is sent to the ADSI telephone in a data burst, which can take several seconds. These commands format information that is on the telephone display and set up softkeys for later use.
This data stream can also be used to load features into the ADSI telephone. A feature is a program that allows the ADSI telephone to operate independently of a host switch or computer. Features can be downloaded to ADSI telephones that are either on-hook, or off-hook.
ADSI telephones cannot pass control statements directly to each other; the ADSI control statements can be generated only by a telephone switch or an IVR, such as Blueworx Voice Response.
A detailed specification for ADSI telephones is provided in the Bellcore Special Report Customer Premises Equipment Compatibility Considerations for the Analog Display Services Interface, SR-INS-002461.
Figure 1 shows an example of an ADSI telephone. Many different designs are available. The areas that are specific to ADSI, the display, and softkeys, can have a range of implementations, but they must meet the following requirements:
- A minimum of 3, and a maximum of 6, softkey buttons
- A display that is 20 through 40 characters wide, and 4 through 33 lines deep
- Optionally, a separate display for softkey labels
Note: The display can be less than 20 characters wide if a mechanism is available to display the characters that are not initially shown on the display.