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From: vances@xenitec.on.ca (Vance Shipley)
Newsgroups: comp.dcom.modems
Subject: Re: Over 1000 cps with PEP?
Message-ID: <1991Jun22.200524.7392@xenitec.on.ca>
Date: 22 Jun 91 20:05:24 GMT
References: <1991Jun19.003439.7587@emperor.scs.com> <1991Jun22.160247.8304@uhura.neoucom.EDU>
Organization: SwitchView
Lines: 24

In article <1991Jun22.160247.8304@uhura.neoucom.EDU> wtm@uhura.neoucom.EDU (Bill Mayhew) writes:
>Our PBX system uses a TDM bus to switch calls.  The system, whose
>type number I don't know, is made by Harris.  Our
>telecommunications engineer tells me that Harris recommends that
>2400 is the highest reliable modem rate that the switch can handle.
...
>Centrex supplied by the telco might behave very differently from
>our PBX experiences.  Centex terminates extensions in the telco's
>switch doesn't it?  If so the grade of equipment doing the
>switching might be higher.  If the switch is a long way away, there
>could be oportunity for signal degredation.

Your Central Office supplying the centrex service also uses TDM (Time
Division Multiplexing).  Digital Central Offices reduce the analog
line to a 64 Kbps PCM (Pulse Code Modulation) bit stream and use TDM
to switch it.

Possibly the Harris PBX is using less than 64Kbps or perhaps there is 
another problem here.  TDM does not preclude baud rates greater than 
2400.


-- 
Vance Shipley     vances@xenitec  vances@ltg  ..uunet!watmath!xenitec!vances