Telecommunications - Configuration of X.25 Physical layer

Connection between the network and the customers premises is by synchronous dataline. The type of dataline will depend on the speed and type of service required.

The following types of connection are available:

Speed Type Interface
2400 bps analogue v.24
9600 bps analogue v.24
48000 bps kilostream V.11 or V.35
64000 bps kilostream V.11

Customers Terminal Equipment must conform to Designation No 89/018S under the Telecommunication Act 1984. (see NET2).

Customers equipment must conform to the electrical interface requirements of the appropriate modem or NTU. In general the following interchange circuits are used:

Configuration and Troubleshooting information

The physical link should remain permanently established, If the user does not wish to make or receive calls this can be signalled by layers 2 and 3 of the protocol (explained later on this document).

Therefore the following circuits should remain permanently ON: RTS, CTS, DSR and DTR.

Transmit and Receive data circuits will continuously send FLAGS (binary value = 01111110) when no frames are being transmitted.

Transmit and Receive Clock circuits, will be used as specified below.

In case of problems, the user should ensure that their equipment is transmitting the correct signals. If RFS, DSR and CD are OFF or clocks and flags are not being received then the dataline may be faulty.

&notes& = yTemporary notes for reviewers

I need to get Chris Wakely to check the modem information (or get a copy of the modem guides myself).


v.24 Interface











Standards:

Mechanical Characteristics: ISO 2110

Electrical Characteristics: V.28,ISO 7498

Functional Characteristics: V.24,RS232,X.21 bis

Procedural Characteristics: X.25 level 2

Maximum cable length between modem and computer: 15 Metres

103 - Transmitted data - From DTE

104 - Received Data - To DTE

105 - Request to send - The DTE should normally maintain this

circuit in the ON conditions.

106 - Ready for Sending - The DCE normally maintains this

circuit ON to signal that data can be

sent on 103.

107 - Data Set Ready - The DCE normally maintains this

circuit ON to signal that data can be

transmitted and received.

108 - CDSL/DTE - The DTE should maintain this circuit ON.

109 - Carrier Detect - The DTE should monitor this circuit and

received data should be ignored if 109

is OFF.

113/114 - TSET - Transmit Clock, options,

a) TSET derived from RSET - recommended

b) DTE independently generate - may be

possible on some modems

c) DCE independently generate TSET - may be

possible on some modems

115 - RSET - Receive clock, Provided by DCE.

&internal&=y




4.2 - rs449 Interface




















Standards:

Mechanical Characteristics: ISO 4902,ISO 4903

Electrical Characteristics:

Functional Characteristics:

Procedural Characteristics:

Maximum cable length between modem and computer:






4.2 - V.35 Interface





Standards:

Mechanical Characteristics:

Electrical Characteristics:

Functional Characteristics:

Procedural Characteristics:

Maximum cable length between modem and computer:


4.3 - V.11 Interface














Standards:

Mechanical Characteristics:

Electrical Characteristics: V.11,X.27,RS-422A

Functional Characteristics: X.21

Procedural Characteristics:

Maximum cable length between modem and computer:


4.4 - Dial Backup


Allows continuity of service during a dataline fault.

When the line is disconnected the loss of carrier signal is detected at the exchange and a backup connection is made to the modem over the Telephone network.

Asynchronous Serial Ports

see this page


metadata block
see also:

 

Correspondence about this page

Book Shop - Further reading.

Where I can, I have put links to Amazon for books that are relevant to the subject, click on the appropriate country flag to get more details of the book or to buy it from them.

cover The Essential Guide to Telecommunications (Essential Guide).

Commercial Software Shop

Where I can, I have put links to Amazon for commercial software, not directly related to the software project, but related to the subject being discussed, click on the appropriate country flag to get more details of the software or to buy it from them.

cover Palm Treo 650 GSM/GPRS Smartphone

This site may have errors. Don't use for critical systems.

Copyright (c) 1998-2015 Martin John Baker - All rights reserved - privacy policy.