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From: chip@vector.uucp (Chip Rosenthal)
Newsgroups: comp.dcom.telecom
Subject: Re: Switched 56kbps services
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Date: 2 Dec 88 01:04:57 GMT
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X-TELECOM-Digest: volume 8, issue 193, message 3

Brian Jay Gould (gould@pilot.njin.net) writes in issue 189:
> I'm trying to get some information on switched 56kbps services [...]
> 1) How do they initiate a call?  via keypad?  AT command set?  [...]
>    I suspect that in most (all?) cases a dedicated link is required
> 2) What kind of link is it?  56kbps digital?  64kbps digital?  T1 required?

Basically the "Switched-56" service is just like a 56Kbps DDS leased line,
except (1) you are charged by connect time rather than a fixed fee, and
(2) it isn't an end-to-end line.  For example, if you have lines into
your Main Street, Elm Street, and Oak Avenue offices and you connect up
from one office to either of the other two.

So, you end up with a 56Kbps dedicated digital line in your facility.
The "dialing" commands are but one of the network control codes which
need to be transmitted over the line.  I believe that the DTE must
generate the dialing commands, unless there are intelligent DSU's which
do this.

Below is information from AT&T's 3/13/87 FCC tariff for Switched-56:

    56kbps Switched Digital Service is furnished for the switching and
    transmission of simultaneous two-way 56 kbps digital signals.  It
    consists of a common user digital network which is furnished between
    designated AT&T Central Offices.  Service is available for use 24
    hours a day, seven days a week.

    A call can access the 56 kbps Switched Digital Service network at
    designated AT&T Central Offices via an access line.  Access lines are
    provided.

    Access lines are connected at the AT&T Central Office for switching to:

    - another access line for communications between two Customer's
      premises served by the same AT&T Central Office, or

    - the common user digital network for communications between two
      Customer's premises served by different AT&T Central Offices.

    Customer equipment is required to terminate a 56 kbps Switched Digital
    Service call.  Technical Publication - PUB 41458 sets forth the network
    specifications of this equipment.

			    __Mileage_Rates__

    Airline			Initial Period		Each Add'l Period
    Mileage			(30 sec)		(6 sec)

    0				$0.35			$0.06
    1-100			$0.36			$0.06
    101-500			$0.38			$0.07
    501-1000			$0.43			$0.08
    1001-up			$0.47			$0.08

Possible documents of interest:

    AT&T TR41458 - Special Access Connections to the AT&T Communications
        Network for New Service Applications, October 1985, $60.00

    AT&T TR41458A2 - Addendum to TR41458, February 1987, no charge

    Bellcore TR-880-22135-84-01 - Circuit Switched Digital Capability
        Network Interface Specifications, Issue 1, July 1984, $48.50

--
Chip Rosenthal     chip@vector.UUCP    |      Choke me in the shallow water
Dallas Semiconductor   214-450-5337    |         before I get too deep.