Specifications
84 Digital Key BX, Digital 400 & Digital 1000 Functional Description
The functioning of the DIGITAL KEY BX, DIGITAL
400, and DIGITAL 1000 systems can best be
understood by dividing each of them into four major
subsystems - control, switching, signaling, and
peripherals (see Figure 38).
CONTROL
The control subsystem is concentrated in the MPD
card and includes one 32-bit microprocessor for
applications and control, and a communications
microcontroller. The microprocessor is responsible for
decision making in call processing functions, for
message translation, for system configuration, and for
running diagnostic routines. The microcontroller is
responsible for communication between the control
subsystem and the peripheral subsystem via the
signaling subsystem.
SWITCHING
All data and audio switching in the system uses digital
signaling. In the Avanti stations, the speech and call
processing tones are converted from analog to digital
signals before being sent toward the system. Digital
signal coming to the Avanti stations are converted to
analog signals in the station.
The digitized audio is circuit switched via the switching
matrix on the MPD card, along the PCM/ TDM
highways. Circuit switched data is also sent via the
switching matrix on the MPD card, along the
PCM/TDM highways.
SIGNALING
Call process signaling such as dialed digits, indications
of onhook and offhook conditions, station status
information, etc. is transmitted from the control
subsystem to the peripheral subsystem via the internal
network.
PERIPHERALS
The peripheral subsystem consists of microcontrollers
on each of the peripheral cards. The interface between
the peripheral units and the main processor on the MPD
card is done via the internal LAN. The tasks of this
subsystem include: conversion of events detected by
card hardware to logical events to be sent to the MPD
and vice versa, and transmission of commands from
the microprocessor on the MPD to the peripheral cards
and stations.
Figure 38 Functional block diagram
Control
Signaling
Switching
Peripherals
Outside
lines
Telephones Optional
peripherals
Internal LAN
PCM Highways