🚀 go-pugleaf

In article <886@epiwrl.UUCP> parker@epiwrl.UUCP (Alan Parker) quotes
jbs@eddie.MIT.EDU (Jeff Siegal) describing how the silences in speech
can be supressed to allow more efficient use of trunks.  He then says:

> Bull.   Very few (if any) trunks work this way.   For the most part
> Digital trunks are TDM mutiplex using either 64K bps per call
> (for regular PCM) or 32K bps (for APCM).   Older analog carrier trunks
> (of which there are still plenty of out there) assign a piece of the
> frequency domain to each call.   These do not have the smarts to move
> calls around during silence periods.
> 
> A scheme like you describe might be used by a carrier on long haul
> (particularly satellite) circuits.   I think the original SBS system
> worked this way (and it didn't work well).

Alan is correct in his assertion that normal interexchange trunks do not
use the technique Jeff described.  The standard acronym associated with
this technique is TASI (Time Assigned Speech Interpolation?).  It was
originally developed for use on high cost routes such as trans-Atlantic
cables (not satellites).  Given the cost of the equipment involved use
is still restricted to this type of application.

A related (but different) way of achieving the bandwidth compression is
packet switched voice which can be found in new products just starting
to enter the market (e.g. StrataComm <sp?>).
-- 
Steve Langdon  ...!{decwrl,sun,hplabs,ihnp4,cbosgd}!amdahl!sjl  +1 408 746 6970

[I speak for myself not others.]