Specifications

S
X-2000 General Information Guide
2
Revision A 5000309
7
• Circuit Switch: Based on messages received from the main control, the switching matrix
establishes paths between parties or between digital processing equipment. The system
circuit links are a shared resource and are allocated to calls as required. The digital signals
are typically PCM voice and various control traffic signals.
• Mass Storage Subsystem: By using the hard disk module, the mass storage subsystem
provides long-term non-volatile bulk memory storage of system information (including
system software, database backup, and logs). Operating system, database upgrades, and
an additional level of backup are provided through a removeable storage device drive.
The peripheral control substantially reduces the computing load on the main controller by
performing all the simple but real-time-intensive tasks that are associated with scanning and
controlling a large number of different Peripheral Interface cards. Following instructions from
the main controller, it sets up connections between the Peripheral Interface cards and the circuit
switch subsystem.
Basic System Architecture
Call Progression
Each telephone connects to the system through an interface circuit on a Peripheral Interface
card. During a simple call, the call progresses as follows:
• When a telephone goes off-hook, the main controller connects the telephone’s receive
path to a circuit carrying dial tone and the transmit path to a DTMF receiver circuit.
• As the user dials numbers (DTMF tones) on the telephone keypad, the DTMF receiver
translates the tones into digits and passes them over message links to main control.
• The main control collects the digits and identifies the destination; then, it rings the desti-
nation by sending a control signal over a message link.