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DCE means Data Circuit terminating Equipment, which can be a modem or one of the
range of Philips SOPHO-SET, SOPHO-LAM or LAM.
A DTE can be connected to the ISPBX using one of the following connections:
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The DTE can be connected to an Analogue Line Circuit (ALC) via a modem. In this case
the modem is the DCE.
ISPBX (ALC) - MODEM - DTE
In this case the ISPBX does not know that a DTE is connected; it is only an extension with
a DNR assigned. Such a DTE can make data calls by sending dial information to the ALC.
The ISPBX establishes a transparent `analogue' speech channel with another ALC with a
modem connected. After answering a normal modem-modem connection is available.
The characteristics of the modem determine the interface type between DTE and
modem, the dialling and answering capabilities (for the call set-up and clearing) and the
actual data transmission of user-to-user information (during the data transfer phase). The
analogue part of the connection is often a limiting factor.
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The DTE can be connected to a Digital Line Circuit (DLC) via a SOPHO-SET, SOPHO-
LAM or LAM. In this case the SOPHO-SET, SOPHO-LAM or LAM is the DCE.
ISPBX (DLC) - SOPHO-SET, SOPHO-LAM or LAM - DTE
The DTE is identified by a DNR. Data is passed between DTEs in a transparent channel.
The fully digital connection offers additional opportunities.
The DTE is not connected directly to the digital line circuit but to a DCE. This can be a
SOPHO-SET, SOPHO-LAM or LAM. The type of DCE determines the interface type
between DTE and ISPBX network, the dialling and answering capabilities (for the call set-
up and clearing) and the actual data transmission of user-to-user information (during the
data transfer phase).
The most common interface type between the digital line circuit and the DTE is V.24.
Most information in this chapter will be dedicated to this type of interface. Most
information will also be valid for the X.21 interface. In a special part in this chapter the
special X.21 information will be discussed.
If an internal data party wishes to be connected to a party in a special type of data network
and the ISPBX does not support the interface type then a gateway is required. Such a gateway
can be connected to a DLC.
2.1.
CONNECTING A DTE TO AN ALC
Digital peripherals can be connected to ISPBX using conventional analogue connections. This
type of digital communication uses modems. The ISPBX does not know there is a digital
terminal connected to the ALC and there is also no need to know. A transparent path between
ALCs can be established irrespective the type of information transferred over the connection;
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