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14
Operator Assistance and
Manual Services
Early telephone networks
were
all
manually operated.
In
the 1950s
automatic
networks
began
to
take over, but even
today
they
have failed
to
supplant
all
manual ‘assistance
services’.
In
the
public network human operators provide
a
‘safety
net’
of
assistance
and

advice
for customers,
and
in
some private networks human
PBX
operators are
still
employed
to
answer
incoming
calls
from
the
public network and
to
connect
them
to
the
required extension. In this chapter
we
discuss
the
operator assistance
services
which
form a
critical

supplement
to
automatic switched services
in
meeting
the
high expectations of today’s telephone customer.
14.1
MANUAL NETWORK OPERATION
In a manual network, the connection of caller to destination is carried out by human
operator. This is done by
plugging
cords into individual line sockets or
jacks,
one
jack
corresponding to each possible destination user. Figure 14.1 illustrates an early manual
switchboard, and Figure 14.2 a typical telephone used on such a manual network.
Instead of a numbered
dial
there is just a cradle for the handset and a magneto
generator to call the operator.
The routine for making a call on a manual network is as follows. The caller lifts the
handset, and rings the magneto generator by turning the handle. This has the effect of
alerting the operator and lighting an
opal
(a light) on the operator’s switchboard
(Figure 14.1).
In
some cases, the operator was alerted merely by rattling the cradle. This

had the effect
of
flashing the opal. There is an opal above each incoming line jack,
indicating precisely which caller wishes to make a call. To answer the request, the
operator uses one
of
the cords mounted on the console part of the switchboard, which is
pulled out and plugged into the relevant
jack
socket immediately below the
opal.
The
operator is now able to speak
to
the caller and ask for the name
of
the person he wishes
to call. The operator records the caller’s name, the destination number and the time of
day, on
a
ticket
for later
billing
of the caller. The destination party is then alerted by the
operator, who rings his telephone with another hand-cranked generator. The connection
281
Networks and Telecommunications: Design and Operation, Second Edition.
Martin P. Clark
Copyright © 1991, 1997 John Wiley & Sons Ltd
ISBNs: 0-471-97346-7 (Hardback); 0-470-84158-3 (Electronic)

282
OPERATOR ASSISTANCE AND MANUAL SERVICES
Opals
and
z=$&.$
Destination
0
Caller Operator
Schematic
l
I
/‘
Generator signalling
crank
Actual
Figure
14.1
Early manual,
or
‘sleeve control’ switchboard
is completed by plugging the other end of the cord into the
jack
of the destination party.
In this way the pair of plugs and the cord connect the two corresponding line
jacks
to
caller and destination. At the end of the call the caller replaces the handset, extinguishing
the
opal.
On noticing this, the operator removes the plugs and cord from the jacks, ready

for use on another call.
To
make calls to customers on other exchanges the operator has a number
of
trunk
line jacks.
To
use them, the operator must relay the call details to the operator on the
second exchange, and forward the connection. The second operator either completes
the call or forwards it to another operator, as necessary. In manual networks, setting up
telephone calls is highly labour-intensive, and in the early days the majority of the
workforce in public telephone companies were
telephone operators.
14.2
SEMI-AUTOMATIC TELEPHONY
Semi-automatic telephony
is the term used to describe connections which are set up by an
operator across an
automatic network.
Semi-automatic telephony was common when
telephone networks were first being automated, especially when some exchanges had
been automated while others remained manual. Callers on the manual exchange, who
wished to call others already connected to an automatic exchange, would have their calls
connected
semi-automatically
by the operator. The caller would first contact the
operator, and the operator would then connect the call onward using special equipment
to control the automatic network rather than routing through further operators.
SEM1;AUTOMATIC TELEPHONY
283

<’
284
OPERATOR ASSISTANCE AND MANUAL SERVICES
Figure
14.3
Inside
of
a hand generator signalling set, showing the magneto coils.
(Courtesy
of
BT
Archives)
SEMI-AUTOMATIC
TELEPHONY
285
Figure
14.4
Early
operator
switchboard.
(Courtesy
of
British Telecom)
286
OPERATOR ASSISTANCE AND MANUAL SERVICES
THE
EXCHANGE
AT
WORK.
A Museum A-side opaator answers and gets into

An explanation whlch will prevent
many common misunderstandings.
toucll with a Hop B-side operator. who finds out
if
Hop 3000 is free and helps the
Museum
operator to
connect the lina.
If
conversely
Hop
3000
wants
The telephone lines
in
a
large
city are divlded
Museum
605.
it
i5
a Hop A-side operator who
answers and
gets
into touch with
a
Mwum
B-de
Operator.

into groups, called Exchanges.
the B-s;dc.
ne
of
M
Exchange
d&
a
Central A-side operator
gets
into
touch
with
a
directly only with
Ringers
up
in
that &change
;
Central
B-side operator.
In every call. therefore,
two
Post
Office
operators.
Bde
with
those

rung-up
in
that Exchange
:
-
.
-
-
__
__
e.g
Muscum
605
wants Hop
3000.
In
reality.
d
coyr.~.
lhst
UI
four
-la
:
1-0
Po.1
o(Lrr
rnma
ud
1-0

.ancun-th.!
i
tk
WO
smhrribs.
-d.
We.
m
I
.n
d.
d
the
um~d
P-
06ec
I&+
ud.
H-
llrr
mea.
-

.
.
4
S
Figure
14.5
The

exchange
at
work.
An
extract from an
early
British
Post
Office publication
providing
an
explanation
which
will
prevent many common misunderstandings.
(Courtesy
ofBT
Archives)
Ironically, in the reverse direction, any caller who was connected to an automatic
exchange would have to dial a code to get hold of an operator to obtain
a manual
connection to any destination customer still connected to a manual exchange.
Manual exchanges have progressively given way to today’s predominantly automatic
networks, but even today callers resort to dialling for
assistance
from the operator in a
number of instances
0
to call a user on a residual manual exchange (particularly in remote overseas
locations)

0
to
receive assistance following difficulty on an automatic connection
0
to receive the answer to a general enquiry
0
to enquire for the directory number of another user
0
to make a call
to
the emergency services (fire, police
or
ambulance)
0
to make a special service call, such as a
reverse-charge call
(also known as
a
collect
call),
or a
personal call,
etc.
CALLING
THE
OPERATOR
287
In addition, many company switchboards and hotels still retain operators for the
connection
of

incoming calls to individual
extensions
or hotel room numbers, despite
the fact that
direct diul-in
(DDI, also
direct inward dialling,
DID) nowadays makes direct
dialling possible.
14.3
CALLING THE OPERATOR
If all we want is to get through to the operator and tell him we need assistance, the effect
of cranking the magneto is very much the same as dialling the right number on an
automatic network. On a
sleeve-controlled
switchboard (one using plugs, cords and
jacks, as illustrated in Figures
14.1 and
14.4),
incoming calls are indicated to the
Figure
14.6
Switchboard operators at work. A picture giving an idea
of
the tangle of hands and
leads
-
the frenetic operation
of
manual exchanges.

(Courtesy
of
British
Telecorn)
288
OPERATOR ASSISTANCE AND MANUAL SERVICES
operator by lighting the
opals.
In modern ‘cordless’ operator switchrooms the call is
administered by
call queueing equipment
or
automatic call distribution
(ACD)
equipment. This equipment stacks up calls in the order in which they are received,
and allocates them to telephone operators in the switchroom as they become free from
dealing with previous calls. Operators simply press a button to indicate that they are
ready to handle another call.
While waiting in the queue for an operator to become free, the caller may hear
ringing
tone,
or may instead be given a recorded message, something like ‘this is the assistance
service: an operator will deal with your enquiry shortly’. Recorded messages have the
benefit of confirming that callers have ‘got through’, giving reassurance that they are
not waiting in vain. The recorded message also allows callers who have accidentally
dialled the number for the operator service (when meaning to dial some other number),
to hang up their calls up and try again.
Because connections made via the operator are multi-link rather than single link
connections, special measures are required, to ensure that the end-to-end quality
of

the
connection is acceptable, and to charge the customer correctly. Callers are normally
connected to the nearest switchroom. This ensures that the end section connection is of
the best available quality. This part of the connection (i.e. from caller to operator) is not
normally automatically metered for charging purposes; the call charges are derived
either from paper
tickets
written by the operator, or from
electronic tickets
produced on
the operator’s computer consoles.
Operator switchrooms are designed to be efficient workplaces, and staff numbers and
rosters are planned to meet customers’ call demand. Just as an automatic telephone
network must be provided with sufficient circuits to meet the traffic, so must the number
of
positions
manned by operators at any given time
of
day match the traffic demand at
that time. A useful quality target for staff providing an operator service is to aim
to
answer all calls within a given time (say 25 seconds), or perhaps to aim to answer 90%
of
calls within say 15 seconds. The latter statistic is often written in shorthand as
PCAl5
=
go%, i.e. the
percentage of calls answered
in
15

seconds=90%. PCA25 can
also be used as a performance statistic (measuring the percentage of calls answered in
25
seconds), but the average caller on a public network who wants operator assistance, is
not satisfied with such a long wait. There is a relationship between the measured value
of PCA and the staffing level of the switchroom, the use of more staff generally
increasing the PCA value. Going to one extreme, to employ a very large number of
operators queueing up to answer calls would ensure almost instantaneous answer. At
the other extreme, with too few operators it is the caller who does the queueing and
waiting.
A
modification of the
Erlang formula
presented in Chapter
30
is called the
Erlang waiting-time formula.
It can be used to calculate the number of operators
required in a switchroom to keep the waiting time down to a target figure (i.e. to cal-
culate
PCA
values)
14.4
OPERATOR PRIVILEGES
In the onward connection
of
calls, operators may be given a number of special
networking privileges. They may have exclusive use
of
particular routes or of certain

TYPICAL ASSISTANCE SERVICES
289
circuits within a route, to give their callers a better chance of getting through than
normal customers (especially when the network is busy). This enables the operator to be
of real assistance to the caller in cases of difficulty, and furthermore reduces the
likelihood of wasted operator time spent in futile repeat attempts. Other privileges
explained below include
manual hold, circuit monitoring
and
interruption,
and
forward
transfer.
However, with the increasing development and automation of networks, and
the small number of human operators available for network
policing,
these features are
becoming obsolete.
Manual hold allows the operator to
hold
the connection even after the calling
subscriber has replaced the handset. This makes it possible to trace the origin of a
malicious call in a case when a caller has given a false identity. It also prevents the caller
making any further calls. This use of the facility
is
now largely susperseded by
calling
line identity
(CLZ)
information in automatic networks and many networks today no

longer have the facility. An alternative use of the
manual hold
facility permits tracing the
cause of faulty connections. The ability
to trace emergency service calls (e.g. fire, police,
ambulance)
is
of special importance.
Circuit monitoring and interruption: sometimes the operator is given the facility to
monitor or interrupt customers calls while in progress. This can be useful in investi-
gating customer complaints, including account discrepancies. It can also be used to
break in on conversation already in progress, when an important incoming call is
received, and this would have been done historically if a trunk call was received while
only a local was in progress (hence the term for this facility,
trunk ofer).
Forward transfer: another facility becoming largely obsolete, the forward transfer
facility allows the operator who has previously established
a semi-automatic connection
for the call, to request assistance from the operator at the destination exchange; inter-
national operators used it to provide
language assistance
(i.e. translation). The oper-
ators might speak an intermediate language (typically French or English) between
themselves and their mother tongue to their own customers to resolve any difficulties
during call set-up. (Example for person-to-person calls). The desired language of
assistance is indicated by a special digit called the
language digit,
which is inserted by
the originating operator’s exchange into the called customer’s dialled digit string during
the signalling at call set-up. This is discussed in more detail later

in
the chapter.
14.5
TYPICAL ASSISTANCE SERVICES
As
most calls are made automatically nowadays, operators need to provide only a range
of
assistance
services to complement the automatic service; here are some of the more
common ones.
‘Station
call’
service
A
station call
is the name given to an ‘ordinary’ call between two telephone stations,
when it is made via the operator. A station call may be made (via the operator as
opposed to automatically) either because the call cannot be dialled directly, or because
customers prefer it, or perhaps because customers have had difficulty in getting
290
OPERATOR ASSISTANCE AND MANUAL SERVICES
through. Another reason may be that the customer wishes to be rung back immediately
after the call has finished to be
advised
of
the duration and charge
(ADC)
(also called
time and charges).
‘Reverse charge’ or ‘collect call’ service

For any of a variety of reasons, callers when travelling may not wish to pay for calls
themselves, preferring to transfer the charges to the call recipients. The service which
does this for them is the
reverse charge
or
collect call
service. The reason for trans-
ferring the charge may be shortage of change when using a payphone, or to avoid
leaving ones host with a large telephone bill when staying away from home. Whatever
the cause, collect call service must always be made via the operator. Before receiving a
collect call,
recipients are asked by the operator whether they are willing to accept the
call charges. If
so,
the call is connected and an operator
ticket
records the call details in
the normal way, except that the bill is sent to the recipient rather than to the caller.
A similar service, self-explanatory, is also sometimes available: ‘Bill call to third party’
(this might allow a payphone caller to charge the call to his home account).
‘Personal call’ service
(Also called a
person-to-person call.)
Sometimes callers may wish
to
contact particular
people who share their telephone with a number of others. A caller may not want to
make an automatic call and pay for a connection, but to find out that the desired
individual is not available. In these circumstances it is appropriate to make a
personal

call,
via the operator. The caller gives the operator the name and telephone number of
the individual required, and the operator then makes the call and checks that the right
recipient is available to come to the telephone. If
so,
the caller
is
charged from the
moment when the operator allows conversation to commence. Usually either a
surcharge or a higher charge per minute of conversation is levied on personal calls. If
the person wanted is not available, the connection is cleared without conversation and
the caller is not charged.
‘Directory enquiry’ service
(Also called
directory assistance.)
To make an automatic call a caller must have the
number of the destination telephone station. Without that number the network has no
indication of what connection the caller wants. If the caller does not know it, perhaps
because he has not called that particular person or company before, then one way of
‘looking-up’ numbers is to use the paper directory, issued to telephone customers. This
gives an alphabetic list of the names of all customers with their numbers. However, the
sheer number of customers nowadays has tempted many telephone companies to issue
only a telephone directory covering the immediately surrounding geographical area. The
operator
directory enquiry
(De)
service
provides a more comprehensive nationwide
service. Access to the service in the normal way is by dialling an access code and waiting
in a queue at the nearest directory enquiry switchroom. The operator looks up the num-

ber in the appropriate paper directory or by
querying
a computerized directory system.
When the number is found it is given verbally to the caller, who then presumably follows
up the enquiry by placing a call over the automatic network. Alternatively the operator
COOPERATION BETWEEN INTERNATIONAL OPERATORS
291
can immediately put a call through. Some network companies charge customers for each
directory enquiry; others give a free service, which they believe stimulates more
automatic calls anyway.
General enquiry service
Whether publicized directly or not, the operator is also often called upon by customers
to answer general enquiries about the telephone or another service. A typical enquirer
might ask for the area code to be used for a particular town, or an international
operator may be asked for the time-of-day difference in hours between originating and
destination countries. The answers
to
these enquiries, and further reference information
to help operators in the undertaking of all their services is usually provided in the
form
of a
visual index $le
(VZF).
This is a handy reference book, kept on each operator’s
console. Operator
tickets
may or may not be made out to record general enquiries, and
charges may or may not be levied.
14.6 COOPERATION BETWEEN INTERNATIONAL OPERATORS:
CODE

11
AND CODE 12 SERVICE
When networks belonging to more than one company are interconnected, there are times
when the operator in one network requires assistance from the operator in the other.
This usually comes about because neither of the operators has quite the same privileged
control over the other network, as they have over their own. Alternatively, in inter-
national networks operators may require no more than language assistance (i.e. transla-
tion of the distant end mother tongue into a comprehensible intermediate language).
To give operators
of
different networks a means of calling one another, ITU-T’s
telephone signalling systems are provided with three signals specifically for the use of
operators; these are
code
I1
signal
code
12
signal
language digit
signal
The
code
I1
signal is used by the operator of the originating network to obtain
assistance from the operator of the terminating network, in cases where the call cannot
be connected semi-automatically because the terminating network is a manual one. The
signal gives access to appropriately equipped operators in the terminating country. In
countries where the network is already fully automatic,
code

I1
service will have been
withdrawn. The
code
I1
signal itself is single digit signal, just as the values
1,2,3,4,
56,
7,
8,
9,
0
are. The difference is that code
11
cannot be dialled by ordinary telephone
customers. This precaution prevents ordinary telephone subscribers from masquerading
as telephone operators, and from using this privileged role to defraud overseas network
companies.
The
code
I2
signal, like the
code
l1
signal, is also used by the operator of an
originating network to get assistance from an operator in the terminating network. Also
292
OPERATOR
ASSISTANCE AND
MANUAL

SERVICES
like the code 11 signal, the
code 12
signal is
a
single digit signal which cannot be dialled
by ordinary telephone customers.
Code 12
is to be used when difficulty has previously
been experienced in establishing an automatic or semi-automatic connection, and it
gives access to an appropriately equipped operator in the terminating country. Unlike
the
code
I1
signal,
code 12
is often used with extra digits.
e.g. (Code 12)
+
ABCD
The extra digits ABCD may be used to identify an individual or particular group
of
operators within a switchroom,
so
helping overseas operators to return to the same
assisting operator.
Code 11
and
code 12
signals are always sent immediately following the country code

and language digit of the international number.
The
language digit
is
an extra digit, inserted into the digit train of all semi-automatic
operator controlled telephone calls to indicate the language that the calling operator
would prefer distant operator to speak in, should language assistance be required.
Not
all countries’ telecommunications companies offer language assistance appropriate to
all the language digits, but the following values are allocated.
1
=
French
2
=
English
3
=
German
4
=
Russian
5
=
Spanish
6
to
9
(spare)
(0

=
dimensioning digit for automatic working)
The
language digit
(LD)
is always inserted immediately after the country code of the
number dialled, or in the alternative position demanded by the international signalling
system. Thus on a call to the number
44
171
234
5678
(a number in Central London,
UK)
the train
44
(1)
171 234
5678
might be used by an operator overseas requiring language assistance from the UK
operator in French. The digit is not inserted by the operator manually, but rather is
systematically added by the exchange on a route by route basis. Thus LD
=
2
for
English might set on the route to Japan and LD
=
1
for French might be appropriate
on a route to a French African colony. When the language digit is set at value

0,
it is
called the
discriminating digit,
and it is used to identify automatic (i.e. non-operator-
controlled) calls. The discriminating digit (value
0
of the language digit) is inserted
systematically by automatic telephone exchanges. Thus the receiving network can
A MODERN OPERATOR SWITCHROOM 293
14.7
distinguish between automatic origin calls and operator controlled (i.e. semi-automatic)
calls. If necessary, and in response to either a
code
11,
code
12,
or
forward transfer
signal,
language assistance
can be given. Having examined the language digit, and in
so
doing performed appropriate routing and call accounting, the international exchange in
the destination country (but not an international transit exchange) will remove the
language digit before sending out the destination national number into the network of
the terminating country. The language digit therefore only exists on international
telephone links.
A MODERN OPERATOR SWITCHROOM
Since the early days of operator-controlled manual telephone networks, operator switch-

room equipment has moved through several phases of technology, first to cordless
boards and latterly to fully computerized systems. It may seem ironic that a computer
system should be designed to work in a mode requiring human intervention rather than
setting out to eliminate the human element; but the fact is, telephone customers still find
comfort in spoken assistance.
Today, computerized operator exchanges give optimized ergonomic conditions for the
human operators without compromising the network efficiency. Some of these exchanges
have a central switching equipment, where the switching and control of circuits takes
place; but in addition, more luxurious remote switchrooms where the operators sit are
connected via computers and computer data links. From their remote switchroom (or
maybe even from a workplace at home) the operators can issue commands, using the
keyboard of a computer terminal, to instruct the central switch what call routing, or other
control action should be performed. Meanwhile the computer can automatically generate
its own electronic tickets, storing the
A
number (callers number),
B
number (destination
number), call duration, time of day, etc. Some of the information can be typed in by the
operator when talking to the caller
(A
party) (e.g. the
B
number), and some of the
information can be derived automatically (e.g. time of day and call duration). Figure
14.7
illustrates schematically the network arrangement of this type
of
computer-controlled
operator exchange.

As
well as the ergonomics and comfort benefits of this type of switchroom (more like
an office, and less like the factory-like switchrooms of the past), there are a number of
other benefits.
0
The operator time required to handle individual calls is reduced.
0
Call re-attempts can be made more easily (by pressing a ‘last number re-dial’
button).
0
The accuracy of operator tickets is improved, and the information is directly
available in a computer format for subsequent computerized bill calculation.
0
The central switching equipment can be located with other automatic exchanges,
and maintained by a common technicial staff, while the switchrooms may be located
near an available workforce.
294
OPERATOR ASSISTANCE AND MANUAL SERVICES
Ewitch location
7

Onward
I
connectio
-
Central
switching
Caller
r
I

I
I
I
I
I
Telephone
clrcuit
Computer
control
link
7
I
Operator
I
I
/
I
Switchroom location
l
L
__
-
_
J
Figure
14.7
Network
schematic
of
modern computer operator exchange

0
If more than one remote switchroom or
homeworking
operators are connected to
the same central switching equipment better staff rostering can be achieved, say by
closing some switchrooms at night, and handling all the overnight traffic at one
switchroom. This was not generally possible in the past.
14.8
OPERATOR ASSISTANCE ON TELEX NETWORKS
The principles
of
telex operator assistance networks are similar to those
of
telephone
operator assistance networks. The difference is that the operator has to ‘speak’ to the
caller through
a
telex machine and not by voice. Other slight differences exist in the
actual menu
of
services offered; for example, the telex operator might offer a multiple
destination service to telex callers.
14.9
OPERATOR ASSISTANCE ON DATA NETWORKS
Operator assistance is not normally available on packet-switched and other data net-
works. However, for the purpose of point-to-point data connection over the telephone
OPERATOR ASSISTANCE ON DATA NETWORKS
295
network, some companies (declining in number) allow their telephone operators, when
asked by callers,

to
select particularly high grade circuits designed specifically for the
transmission of voice band data. The customer uses such circuits in conjunction with
data modems located
on
the customer premises at either end
of
the connection.