5 Translate the following sentences into Russian:

1 The operator connects the call by plugging into the jack on the switchboard corresponding to the called customer's line.

2 The structure of a switch is an odd number of layers of smaller, simpler sub switches.

3 Each voice channel is represented by a time slot (say 1 or 2) on a physical wire pair (A or B).

4 Each subscriber telephone number required an individual pair of wires from the switch to the subscriber's phone.

5 Telephone switches are a small part of a large network.

6 The first Electronic Switching Systems were not entirely digital.

7 Multi-frequency (MF) was the last of the pre-digital methods.

8 Circuits connecting two switches are called trunks.

Text 3

Public Data Networks

Public Data Networks are designed for data transmission only. They therefore avoid the limitations of speed etc. of transmission over the switched public telephone or telex network. The Public Data Network is a circuit-switched type of digital network and its basic purpose is to provide a means of synchronous data transmission.

The data switching exchange (DSE) controls the set-up and clear-down of data calls, and monitors the connections and functions of the network. This exchange, which is capable of handling 100 calls per second, may be supplemented at a later date with a special service centre (SSC) for the introduction of certain new facilities. The DSE is connected to a data circuit concentrator (DCC). The purpose of the concentrator is to collect traffic from a number of individual subscriber circuits. This traffic is passed via time division multiplexed high-speed links (TDM) to the exchange. These TDMs, which consist of time division multiplexed streams (64 Kbps), also transfer traffic between the DCC and one of the multiplexers (RMX). The multiplexers (RMX and DCC) connect several subscriber lines either directly to the DSE or to the DCC which passes traffic to the DSE. Between the RMX and the data terminal equipment (DTE), the data circuit terminating equipment (DSE) is located in the subscriber’s premises. It primarily provides the standardized interface between the DTE and the network. Lastly, the DTE, which consists of a printing or alphanumeric visual display terminal or a computer, provides the subscriber with the data reception facilities.

EXERCISES

1 Answer the following questions:

1 What are the functions of the following components:

DCC……………………………….

RMX/DMX………………………….

DSE……………………………….

DCE……………………………………

SSC…………………………………….

TDM………………………………………..

DTE………………………………………

2 What is the advantage of data networks compared with data transmission over the telephone?

3 What is the capability of the DSE?

4 What does the terminal equipment consist of?

2 Match the facilities with the appropriate description:

1 abbreviated address call	a) on dialing, the subscriber is always connected to a pre-determined number.
2 direct call	b) the same number is used for several equivalent terminals. The connection is made to a free terminal.
3 closed user group	c) a number of subscribers are protected against calls from subscribers outside the group.
4 outgoing calls barred	d) the subscriber cannot call other subscribers.
5 group number	e) the subscriber uses only 2-digit numbers for a limited number of other subscribers.
6 connect when free	f) the subscriber is informed of the cost of a call on completion of a call.
7 charge advice	g) a call to an engaged connection is put in a queue and established when it becomes free.