CERN - DATA HANDLING DIVISION CERN/DD/DH/69/27 B.W. Evershed December 1969

THE COMPUTER AND THE TELEPHONE

Summary

In response to a need for a computer job enquiry facility, a

job-enquiry-by-telephone (JET) system is discussed in some detail. Some

of the general problems and possibilities presented by interconnecting

the telephone and computer are also discussed,

DD-eel

CONTENTS

1. INTRODUCTION

2. THE TELEPHONE AS A COMPUTER I/O DEVICE

3. THE COMPUTER AS A TELEPHONE EXCHANGE PROCESSOR

4. A JOB-ENQUIRY-BY-TELEPHONE (JET) SYSTEM

5. CONCLUSIONS

6. REFERENCES

1. INTRODUCTION

The telephone has been the conventional method of communication

between people for several decades. The computer has been with us for

well over a decade necessitating from its conception communication with

people. The telephone network is being used increasingly for data transmission

between special terminals, which are connected to the telephone line via

'modems'. These modems convert the d.c. signals of the terminal equipment

into a.c. signals for transmission over the telephone line. As yet,

however, little use is made of the telephone handset itself as a means of

communication between people and computers.

Interconnection of a computer system and a telephone system can be

considered from two standpoints:

- the telephone as ax1 I/0 f ac ili ty for a com put er,

- the computer as a processor for the telephone system.

2. THE TELEPHONE AS A COMPUTER I/0 DEVICE

The conventional telephone may be considered as an I/0 device

for a special-purpose computer - the telephone exchange. It will be many

years before a computer will be able to interpret human voices, consequently

any information input to a computer must be in a form which can be easily

converted into a digital form. For us, it will be even longer before we

can directly interpret digital data, so computer output must be converted

to audible messages or tones.

Connection to a computer via telephones using this combination of

digital and analog transmission is now being used under such names as:-

ARU - Audio Response Unit (Ref. 1)

VRS - Voice Response System (Ref. 2' 3)

DIVA - Digital Input, Voice Answer (Ref. 4)

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Until recently for normal communication the dial telephone has

been universally used, however this is now being replaced by the push-

button telephone (Ref, 5). In the United States a third of the exchanges

are already equipped for dealing with push-button telephones. In Europe

it will be some years before they are in general use, although a few are

already in experimental use (Ref. 6) and the latest Swiss exchanges, including

CERN's can be adapted for push-button telephones.

The push-button telephone was developed to increase dialling

speeds from an average of around 0.7 digits/s for a rotary telephone to

some 2 digits/s with a push-button telephone. The dial telephone produces

a train of d.c. pulses, but the push-button telephone produces a combination

of two-out-of-eight frequency tones.

2.1 Telephone I/0 Characteristics

As an input device

The dial telephone can generate both digital (dialled) and

analog (audio) information. The digital information is given as a train

of d.c. pulses at approximately 10 pulses/s repeatable on average at the

rate of 0.7 digits/s.

The push-button telephone does not generate any d.c. pulses.

All 'dialling' signals consist of fixed frequency tones (Ref. 5). Each

time a button is pressed, a tone signal is generated consisting of two

frequencies selected out of a total of eight possible frequencies in the

range 700-1500Hz. The digits can be generated at a maximum rate of approx­

imately 2.0 digits/s. Push-button telephones destined for data generation

are usually equipped with two extra buttons for control function, a typical

use is to generate alphanumeric data, with these two buttons being used in

a similar way to the figures/letters shift key of 5-unit teleprinters.

The bandwidth for audio input for both types of telephone is 300

to 3000Hz.

As an output device

The outputs received are analog (audio) or digitally coded

analog signals 0.f. busy, unobtainable etc., tones) also in the 300 to

3000Hz bandwidth.

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2.2 Computer Input from a DiaJ. Telephone

When a telephone number is dialled in the normaJ. way from a diaJ.

telephone, the dial pulses travel through any intermediate exchanges and

terminate in the exchange of the number being caJ.led, but do not arrive at

the distant telephone.

There are, however, two techniques which do aJ.low these dial

pulses to arrive at the distant telephones

2.2.1 Pulse transmission before establishing connection

When a caJ.l is made from inside CERN to Geneva, the initiaJ. 10 1

selects a special line which permits further dial pulses to be transmitted

to the outside exchange (Vernier), and only when the extra 6 or so digits

have been diaJ.led is the connection established ready for audio signals.

A similar method could be used for transmitting code pulses to a

computer. The first digit would select a special line which when free would

reply with a 'go ahead' tone (c.f. calls to Geneva). The further digits

would then be dialled and the computer would reply with anothe 'code

received' tone, only then would the connection be established ready for

audio signaJ.s transmission.

The receiver for these pulses uses standard telephone circuitry.

A line relay detects the pulses, and the line switches over to an audio­

transformer for transmission of audio signals.

A system using this technique has been instaJ.led in Berne for the

remote control of dictating machines.

2.2.2 Pulse transmission after establishing connection

If a number has been dialled in the normal way, after the connection

is made the dial can be used again to generate decimal coded pulses (Ref, 7),

But the exchange has a low frequency cut-off and the square pulses get

differentiated at the exchange and at the receiving end only 'spikes' are

received. Provided that these signals have passed through only one exchange

they are easily detectable. If calls are made from outside CERN, but in

the Geneva area, then the signals will pass through one or two exchanges

but may still be usable. For calls from further away the signals are more

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distorted and become unusable.

Detection of these pulses involves some tricky electronic

circuitry which must compromise between missing weak pulses and accepting

noise as pulses. The line termination and switching is of course as for a

normal telephone.

Systems using this technique are in use in Germany (Assmann

dictating machine, IBM audio-response equipment) and in Switzerland where

the PTT have installed an experimental automatic waking service in

Solothurn.

2.3 Computer Input from a Push-Button Telephone

Here the transmission problem is greatly simplified since the

digital information can be sent as audio-frequency tones through the normal

voice-communication path right through all the exchanges, repeaters etc.,

to the far end.

At the receiving end the 2 out of 8 frequences must be detected

and can be directly converted into a 2 out of 8 binary code. In the U.S.

data sets are available e.g. Bell 403 (Ref. s, 9) which decode the

frequencies into a 2 out of s, a 4-bit binary code, or to an ASCII code.

There is also a voice answer-back path in the other direction for such

applications as computer voice response systems.

We have had several discussions with Swiss-PTT engineers and they

consider all three types of data transmission to be feasible.

3. THE COMPUTER AS A TELEPHONE EXCHANGE PROCESSOR

Telephone switching technology is slowly advancing through the

Strowger, Cross-bar, Reed-Relay, Solid State and PCM* techniques in order

to achieve higher speeds, reliabilities, densities etc. With PCM being a

digital technique and with more facilities being demanded, computer-like

equipment is now being used in telephone exchanges.

* Pulse-Code-Modulation

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Examples of the facilities envisaged are:-

- an Automatic Waking Service, whereby the extension number and

time to be called are entered from the telephone dial and the

computer memorises these and calls back as requested with a

recorded message.

- Simple Calculating Service, allowing simple calculations to be

entered from the dial and the computer 'speaks' the answer.

In Switzerland at least one telephone manufacturer (Hasler) is

producing their own special-purpose computer system (Dataflex) for providing

such facilities within the telephone service.

An electronic telephone exchange using thyristor switches has

recently been announced by IBM (model 2750). It is designed to provide the

normal telephone switching functions plus many data transmission facilitief:;.

Many of the functions previously wired in, such as allocation of extension

numbers, re-routing of incoming calls, recording traffic statistics etc.,

are controlled by a stored program which can be easily modified from a

keyboard. The data transmission facilities include: checking validity

of character codes and message lengths, data storage on punched tape, audio­

response from remote computers, data capture etc.

4. A JOB-ENQUIRY-BY-TELEPHONE (JET) SYSTEM

As part of a study of ways of implementing a job enquiry system,

a proposal was made to use the telephone handset as the enquiry terminal.

The object is to allow anyone who has access to a telephone to be able to

interrogate a computer as to the status of a particular job in the computer.

Briefly, the operation would be that the caller would dial a

string of digits corresponding to the job's 'account' number and then

would hear recorded messages which the computer has selected, indicating

whether the job was awaiting input, in execution, awaiting output etc.

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System Requirements

are:-

In planning a job enquiry system some of the points to be considered

1 What size the message repertoire should be

2 - How many telephone lines from JET to exchange are required

3 - To which computers JET should be connected

4 - Digital vs. Analog storage Of the messages

5 - JET/Computer Interface

6 - JET/Telephone Interface

7 Whether job statuses should be stored in JET

8 - Should JET be able to call the user

9 - Access to JET from telephones outside of CERN

10 - Multilingual messages

or Computer

4.1 Message Repertoire

ways: -

A job could be given five possible statuses:

1. Not read-in by card reader, i.e. not known

2. Ready and waiting on disk in the input queue

3. Being executed

4. Executed and waiting on disk in the output queue

5, Finished and output

For statuses 2 to 5 additional information of interest is:

For 2 and 4 - its position in the queue

3 - how long it has been in execution

5 - when it was finished

This supplementary information could be output in different

a) By a series of 'pips' giving a quantitative answer for low order numbers

(say <5) and a qualitative answer for higher values.

b) A number composed of individually spoken digits (e.g. 'three-five' for

thirty-five) requiring a repertoire of 10 digits.

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c) A normally spoken number, requiring a repertoire of 28 spoken digits

(0 to 19 and 20 to 90) for all numbers 0 to 99.

Taking solution 'b' as the most practical, this would require a

total repertoire of 17 phrases ( 1 0 1 to 1 9 1 and 7 messages). It is

proposed that the five status messages would be output in three parts,

separated by pauses as follows:

1st part pause 2nd part pause 3rd part

'Job not known' - -

'Job in input queue 1 to 99 1 jobs to go'

'Job in execution' 1 to 99 I minutes so far'

I Job in output queue 1 to 99 I jobs to go'

I Job done at' 0 to 23 O to 60

The total message length would be about 5,5 seconds.

4.2 Multiple Telephone Lines

It is necessary to determine if more than one telephone line

between the exchange and. the JET are necessary to avoid the system being

too frequently 'engaged'. A satisfactory service would probably require

an "all-lines"'"'.busy" probability to be around 0.1.

The probability that it will be engaged depends on:

Number of lines

Call duration

Max. call frequency

Probability of 1 line busy

Probability of all 'n' lines busy =

n

t min.

f calls/min.

busy time total time ctf)n

n

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Calling Frequency

Previous studies have shown past workload peaks to be around twice

the mean, let us allow for a peak of up to three times the mean.

jobs/day.

With currently up to 1000 jobs/8 hour day, let us allow for 2000

Assume a max. of 5ofo of jobs will receive an enquiry

Mean call frequency

Max. II If

2000 x • 5 8 x 60

3 x mean

2 calls/min.

6 calls/min.

Call Duration

Ref. 1):

The breakdown of events for a call is as follows (*figures from

Dial JET digit and await 'ready' tone 2.5* s.

Dial 10 'account no.' digits 13.0

I/P data rate (10 ch/sec) x 10 1.0

Search job tables and generate reply 2.0

Output data (4 ch) 0.4

Messages 5.5

Hang-' UP 5.0*

29.4 s.

Whence the Call Duration~ 0.5 minutes

B b b .1 .t (6.0 x 0.5)n usy pro a i i y = n

let the number of lines 'n' be 5

then Busy Probability 0.078

whence at least 5 lines allowing 5 simultaneous communications

would be necessary.

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4.3 Multiple Computers

At present the computer service is assured by the 6500 and 6600,

later there will probably be other computers which may not be compatible

as seen by the user.

1.

2.

3.

For interrogating several systems there are three possibilities:

One JET could be connected to one computer which is informed of

the job flow in the other machines, e.g. through FOCUS on the

3100 or a separate 'house-keeping' computer.

One JET equipment could access any of the computer systems.

A separate JET System for each computer system.

To select which computer to interrogate there are again two

possibilities:

a)

b)

1.

2.

If the computers have incompatible operating systems (unlike the

6500 and 6600) the user will know beforehand on which system his

job will run and consequently could add a computer code number

to the digits dialled, or in case 3., could dial the corresponding

JET number.

Otherwise, the interrogation can only be done sequentially,

preferably in order of decreasing probabilities of finding the

job.

4. 4 Digital vs. Analog Message Storage

Two methods of storing the messages are used:

Analog storage on tape, drum etc. (Ref. 2).

The voice analog signal is coded and stored digitally within the

computer (Ref. 1). To output the messages the coded data is

passed through a digital-to-analog converter. To avoid

intermediate storage the digital data is generated as the message

is being heard.

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The digital coding corresponding to the audio signals must be

generated and recorded by a specially built analog-to-digital sampling

converters.

The analog method is the more expensive, whereas the digital method

uses much more computer memory capacity and output channel time.

4.5 JET/Computer Interfaces

As already explained the JET system should be able to communicate

with several computers, initially these would consist of the 6500 and 6600,

later however there may be other machines of other makes.

Any supplier of equipment for the JET system is unlikely to be

prepared to supply an interface compatible with all the computers (unless

CDC would be the supplier of both the JET equipment and of the future

machines).

Consequently, we must expect some of the interfaces to be specially

designed by CERN. For connection to the 6000 machines the simplest hardware

interface would be to a multiplexor sub-channel, al though it would be quite

feasible to make a 3000-type interface and for connection to the 3100 an

interface with the on-line HP 2116 could be made.

4.5.1 Input to computer

The information to be transmitted to the computer would consist

of some 11 decimal digits. (1 line number, 10 job account number.) The

average duration of a call would be around 30 seconds, if the data input is

allowed 1% of this time, the input rate should be approximately 30 words/

second. The word width should be at least 4 bits to allow for decimal

digits from the telephone.

4.5.2 Output from computer

The information to be transmitted from the computer would consist

of six codes (1 line number, 5 messages). The number of lines is unlikely

to exceed 8, but with 17 different messages a word width of 5 bits would be

necessary.

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Again allowing 1% of the total 30 seconds for this data output

requires a data rate of 18 words/second.

4.6 JET/Telephone Interface

Since the object is to allow any user to call the computer

from his office telephone, any method using modems would be exhorbitantly

expensive (~ 4000 Sw.Fr./modem). As already seen (2.2) there are techniques

for using unmodified telephone handsets.

The interface itself

The detailed design depends on the characteristics of the JET

equipment, but basically it must do the following functions:

generate a 'go ahead', 'busy' and 'out of service' tones

detect the dial pulses and pulse trains count and store the

decimal codes dialled

transfer decimal codes to JET in handshake mode

generate 'number accepted' tone when signalled by JET

relay audio signals from JET back to the caller

It may well be preferable to divide the interface into telephone

and JET halves. A telephone half doing the pulse selection and tone genera­

tion using telephone techniques (relays, transformers) and a computer half doing

the counting, storage and transfers with computer techniques (semi-conductors).

In any case the PTT would insist that the telephone end of the interface

be approved by them.

4,7 Job Status Stored in JET or Computer

Currently all job status information is stored within each

computer. If the JET control were done with a computer-like device, the

job status information could be collected from all computers and held in its

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own store.

4.8 Answer :Back or Call :Back

In the past, automated information answering systems (e.g.

public weather service) have answered back immediately or not at all. It

is quite feasible for the caller to include a telephone extension number

with the job account number, this would enable the JET to either call back

when free, or to call back when the job is finished - providing, of course,

that the JET equipment is equipped with an automatic dialling facility.

4.9 Access from Outside CERN

It seems a useful facility ( to some!) to be able to call the

computer via JET from home or elsewhere outside CERN. With the existing

equipment in the Vernier exchange it is not possible to pass on the extra

digits when they are dialled with the extension number (2.2.1) from outside

CERN. This could however be sent once the call is established from a dial

telephone, (2.2.2), or from a push-button telephone if the callers exchange

permits them.

4.10 Multi-lingual Messages

It would be quite feasible to include a 'language' digit in the

input. With an extra message repertoire for each language, the output

could be selected from the appropriate repertoire according to the language

digit.

5. CONCLUSIONS

The telephone system will increasingly use computer techniques

and computers will increasingly use telephone networks and telephone hand­

sets.

There are three techniques available for transmitting digital

information from the telephone hand-set to a computer; two for dial

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te1ephones and one for push-button telephones.

A computer job-enquiry system accessible from any telephone

within CERN is quite feasible. A survey is being made of possible solutions

using specially designed and commercially available equipment.

6. REFERENCES

1. IBM

2. CDC

3 •.

4. S onderberg

5. Davisson

6. Tournay et al

7. Marill et al

"IBM 7772 Ausio Response Unit" IBM A27-27ll

"Multiplexed Voice Response System" - CDC 36077100

"Telephone Voice Response System"

Automation - November 1966 p. 47

"Machines at Your Fingertips"

Record p. 199 - July 1969

Computers and

Bell Laboratories

"A push-button telephone for alphanumeric input"

DATAMATION -

April 1966 p. 27

"Un terminal economique pour la transmission de donnees"

- colloque int. sur la teleinformatique - Paris 1969 p. 231

"Data-dial - two-way communication with computers from

ordinary dial telephones" Communication of the ACM -

October 1963 p. 622

8. Sonderberg et al "The TOUCH-TONE telephone - transmissions of Digital

9. Bell System

Information" IEEE transactions on communications

technology - p. 812 December 1967

"Data Set 403D, 403E Interface Specification"