Digital Signal Processors
A major feature of VISM is the array of Digital Signal Processors (DSPs) that provide extensive voice signal processing capability.
Each VISM contains 37 DSPs. Twelve are general-purpose and can be configured to perform echo cancellation or data compression. Twenty-four can be used for data compression only. One DSP is a Jukebox DSP that is used to load code (program) overlays to the other 36 DSPs.
In addition to the DSPs, one HDLC controller is used for CCS signal processing.
Together, the DSPs support the DS0 channels of the eight T1/E1 lines.
A timeslot interchanger routes the DS0s to
A data compression DSP or
An echo cancellation DSP and then a data compression DSP or
The HDLC controller (for CCS processing)
DSPs are loaded with their programs at boot time.