A Consumer’s guide to Calling Line Identification services
(2nd edition February 2001)
Foreword
What are Calling Line Identification services?
F1
Most telephone users know that when you dial 1471, you can find out who made the
last call to you. This service is called Call Return. It is also possible, if you have suitable
equipment, to subscribe to a service where the caller’s number is displayed on your phone, or
an attachment, before you answer the call. This is called Caller Display. These services were
first introduced in November 1994.
F2
Caller Display and Call Return are both services which feature the ability to identify
the caller’s number and are known as Calling Line Identity (CLI) services. These services
can give you more peace of mind when using the telephone and are a welcome development,
but there may be situations where callers may be concerned that others may see or find out
their number. In most cases, this shouldn’t be a problem and callers can get benefits from
CLI services, since, if a call isn’t answered, it may be possible for the called customer to see
or find out the caller’s number and return the call. In a few cases, callers will want to
maintain the anonymity that the telephone service traditionally used to have, so all customers
have rights to maintain their privacy if they feel this is important.
F3
Chapter 1 of this Guide describes your legal rights to privacy and the implications of
these choices. It covers:







call blocking by dialling 141
line blocking
overriding line blocking by dialling 1470
your rights under the Telecommunications (Data Protection and Privacy) Regulations
1999
the Call Return and Caller Display services
the Telephone Preference Scheme
the use of Presentation Numbers.
F4
In Chapter 2, more details are described which will be of interest to business
customers who may wish to use CLI services to improve the way they use their telephone
system and thereby assist their business. It covers:





CLI on PABX systems
far end breakout
indirect access
smart boxes
call centres
 the role of Service Providers.
Chapter 1
Advice for residential users
1.1
Calling Line Identity (CLI) services, such as Caller Display and Call Return, use a
feature of modern telephone networks which transmits the number of the caller as each call is
set up. Called customers, using these new CLI services, can now have access to this
information. With Caller Display, they can see the number on their phone before answering
the call, while with Call Return, they can dial 1471 at any time to find out the number of the
last caller to their number, whether it was answered or not.
1.2
In some situations, callers will want to continue to have the benefit of the anonymity
that the telephone system had in former times, so all customers have the right to withhold
their number when making calls. In this Chapter, your rights to this privacy are described and
the consequences of these choices explained.
1.3
Many customers feel more confident about receiving calls now that they can find out
who is calling and consequently may feel less confident if their callers use this privacy
feature. This booklet also explains what your rights, as a called customer, are in this
situation. An important point to appreciate is that if the caller does choose to withhold his or
her number, it prevents you from seeing or finding out their number, but it doesn’t stop your
phone company from having access to this information. CLI has long been used in modern
phone systems to allow the phone company to trace malicious or nuisance calls and it also
forms an important part of the 999 emergency service, allowing the emergency operator to see
the caller’s number should the caller be unable to communicate with the operator.
1.4
However there are strict rules about the uses that a phone company can make of a
caller’s number if it has been withheld, and about who, within that company, has access to it.
Essentially employees within a phone company should only be able to access and use a
caller’s withheld number in circumstances where that information is essential so as to be able
to provide a phone service. For example, when someone calls operator assistance to seek
help in connecting a call or to report a fault it is reasonable that the operator should be able to
see the caller's number. It would not be reasonable, though, for a caller’s number to become
visible simply because he or she phoned to ask about additional services that the phone
company provides. And in no circumstances may the phone company use a caller’s withheld
CLI information for marketing purposes.
Your rights as a caller
1.5
Because the use and availability of a caller’s CLI information raises important privacy
issues the European Telecommunications Data Protection Directive (TDPD) protects the
privacy of calling and called customers by setting out a series of legally enforceable rights.
These rights were brought into United Kingdom law by the Telecommunications (Data
Protection and Privacy) Regulations 1999 which entered into force from 1 March 2000 and
are enforced by the Data Protection Commissioner. The rest of this section looks at each of
these rights in turn.
The right to withhold your CLI
1.6
Normally, when you make a call, your number will be available to the called
customer, using either the Caller Display or Call Return (1471) services. It is both polite and
helpful to others to let them have this information as it can give them more confidence when
answering phone calls and they may be able to phone you back later.
1.7
However, there may be situations where you don’t want those you call to find out your
number. The simplest way to do this is to dial 141 before the number you want. So, if you
want to dial, say, 020 7634 8700 but want to withhold your number, you would dial 141 020
7634 8700. Always dial the 141 first, in front of any other numbers. However, if you are
dialling from an extension on a business switchboard system, where you have to dial
(typically) 9 for an outside line, you should dial 9 first, then 141 and then the outside number.
1.8
Under the law, telephone companies must now offer all users a free service which
enables them to withhold their number in this way on a call-by-call basis.When you dial 141,
this is described as call blocking , or ‘blocking your CLI’. As mentioned above, it stops the
called customer from knowing your number, although your phone company and its
employees will still be able to see it where this information is essential to enable them to
provide you with a phone service.
1.9
In a very few situations, you may wish to block your number on all calls. Instead of
having to dial 141 on each call, you can request your phone company to provide you with a
service called Line Blocking of CLI. Under the Directive this service too must be made
available free of charge to all subscribers, ie any person who has entered into a contract with a
phone company to receive telecommunications services. With line blocking your number will
be withheld on all calls made from the line that has line blocking on it. As a result all your
calls will remain anonymous to those you call. This service is useful in situations where it is
vital to maintain your privacy, but there are drawbacks to this service. Some people you call
may not wish to answer calls where you have withheld your number or they may feel nervous
about doing so. They may have access to a service which won’t even connect calls to them if
the caller’s number is withheld. Therefore you should allow your number to be known
wherever possible. In situations where you have elected to have you number permanently
blocked, it is nevertheless possible to send your number if you need to. To do this, you need
to dial 1470 before the number you wish to call.
1.10 When you do allow your number to be accessible to those you call, they can use this
information to make a call back to you, so don’t be surprised if someone calls you back, even
if your original call went unanswered or you didn’t give the person your number. People who
receive your number in this way may not, by law, use it in a way which affects your right to
privacy. Those who retain an individual subscriber's telephone number are likely to hold
personal data subject to the Data Protection Act 1998. Annex A provides more information
about what your number can and cannot be used for. Because of this, you can allow your
number to be accessible, but you can be confident that it is not used for purposes you would
not approve of, or be passed on to anyone else.
1.11 Some people you call may have their phone service provided by a different phone
company from yours. In many cases, your number can still be sent to them, so they can also
benefit from accessing your number. All phone companies are bound to ensure that if you
withhold your number, this applies on all calls, even ones that pass to other phone companies.
So, if you need to withhold your number, you can do so in complete confidence that nobody
you call can access it, whatever phone company they may be on.
1.12 So, in summary, you have the right, guaranteed by Data Protection laws, to withhold
your number, either on a call-by-call basis using the 141 code, or by special arangement, on a
permanent basis. You need to think about the impact of your privacy actions on those you
call. It is polite to treat other customers as you would like to be treated, so let others have
access to your number whenever possible.
Your rights when called
1.13 Most phone companies provide the Call Return service, where you can dial 1471 to
find out who last called you. It is usually possible to find out the date and time of the call
and, by pressing 3, to make a return call. If the caller withheld his or her number, you will be
informed of this. 1471 calls are free of charge, but if you use the return call feature, your call
will be charged in the normal way.
1.14 Sometimes calls are not able to deliver a number for the caller, for example on some
calls from older mobile phones, on international calls, or calls from other phone companies
that have not implemented any CLI services. On such calls you will be informed that no
number is available.
1.15 In future, you may be able to dial a freefone number so as to erase the record of who
called, so that others who have access to your phone and who might later dial 1471 cannot
find out who called you.
1.16 Many phone companies also provide the Caller Display service, for which a rental
charge is made. To use this service, you will also need to buy a suitable telephone, or display
attachment, which will allow you to see the number of calls before you answer them. Such
telephones usually have a memory feature to keep a record of a series of calls made to you.
When buying a Caller Display telephone or display attachment, you may need to check that it
is compatible with your phone line, as some phone companies use a slightly different
arrangement to deliver CLI numbers. However, many display phones can work on all UK
networks.
1.17 The advantage of the Caller Display service, over using 1471, is that you can see who
is calling you before you answer, so you can chose not to answer the call, if you wish, or
perhaps leave the call to be answered by an answering machine, if you have one. When you
use the Caller Display service, your phone will display not only the number, but also the date
and time of the call. It will also usually display the text WITHHELD or UNAVAILABLE
when a number cannot be delivered. The phone may be able to associate the number received
with a directory of names of your frequent callers which you have stored in the phone’s
memory.
1.18 Occasionally, other words may appear, such as PAYPHONE, INTERNATIONAL or
OPERATOR. While this can be helpful in explaining why the caller’s number is not
available, you should be aware that this text is not always consistently displayed on calls from
payphones, from abroad or from the operator. In future, callers’ numbers may become
available even on international calls.
1.19 When you receive callers’ numbers, you may use them to decide how to handle the
call or to make return calls. But as explained above, these numbers are personal data and you
must not use the information for other purposes unless the caller has given his or her
permission. Annex A gives further information on this.
Anonymous Call Rejection
1.20 In some circumstances, you may find that you receive more calls where the caller’s
number is withheld than you are comfortable with. If these are sales calls, you may wish to
register with the Telephone Preference Scheme (TPS) which should reduce such unwanted
sales calls. It is an offence for a company to make sales calls to a person who has registered
their number(s) under the TPS. You may contact the TPS by phoning 0845 070 0707 .
1.21 However, for other situations, your phone company is now required by the Directive
to provide a service which prevents ‘withheld’ calls from getting through to you, known as
Anonymous Call Rejection (ACR). With this service, callers who withhold their number hear
an announcement saying that you do not wish to receive calls where the number is withheld.
Calls, which for other reasons, cannot provide a number, that is, where the number is
‘unavailable’ are not blocked by this service..
1.22 ACR is sometimes known as ‘Block Blocking’ because it allows you to block those
calls where the caller has blocked their number. You need to think carefully before opting to
use this service, as many customers withhold their number for quite innocent reasons,
especially in cases where no return calls can be made. One example is a hospital payphone
on a bedside trolley, but there are many others.
1.23 Although the Directive now requires phone companies to offer an ACR service, there
are technical reasons why this is not currently a practicable option on digital services such as
ISDN or GSM (digital mobile). Although work is being carried out to write the technical
standards necessary to implement the service they are not yet available. A further problem is
that some of the signalling systems used by digital services are not yet capable of
distinguishing between calls where the CLI has been ‘withheld’ and those where it is
‘unavailable’. Until the necessary standards are in place it may be possible, in some cases, to
reject calls using a customer’s own equipment. most mobile handsets, for example, allow you
to accept or reject a particular call.
Presentation Numbers
1.24 Where numbers are available for display or access via 1471, you can have confidence
that they represent the number of the person calling you. In some cases, where calls come
from businesses with private switchboards, the number displayed might be the number of the
switchboard operator, rather than the extension calling you. In other cases, the actual
extension number may be displayed. There may be instances where the number is different
from the actual calling line: this is known as a Presentation Number. These are used when
the actual calling line is not appropriate for receiving return calls, for example when a call is
made on an “outgoing only” line or when an organisation uses different phone companies for
outgoing and incoming calls.
1.25 However, Presentation Numbers are only allowed in controlled circumstances so you
can be confident that the identity of the caller or his company is always correct.
Connected line identification
1.26 Some modern equipment connected to ISDN lines is capable of displaying the actual
number to which a call has been connected, which may differ from the number dialled. This
is known as Connected Line Identification. For example a doctor may have calls forwarded
from their surgery number to their home number at certain times. However they may want to
keep their home number private. To cover this situation the Directive offers called customers
the right, free of charge, to prevent the caller from receiving the number to which a call has
been connected.
Charitable helplines
1.27 The Directive also gives subscribers the right not to receive CLI information about
incoming calls. Although this right applies to all subscribers, in practice it is of most use to
charitable helplines which wish to guarantee the anonymity of their calling clients.
Reasonable use of this service must be provided free of charge.
Chapter 2
Advice for business users and telecoms professionals
2.1
This chapter is designed to give you more information about CLI services, to allow
businesses and professional telecoms people to make the most of these services. It is
advisable to read Chapter 1 first, as this contains important advice for all telephone users.
2.2
As a business customer, you may be using more complex telephone equipment than
the residential customer, such as ISDN terminals, mobile phones, Private Automatic Branch
Exchanges (PABXs, referred to in Chapter 1 as ‘business switchboards’) or Call Centres.
Choice of telecommunication networks
2.3
As a business user, you might well be using, or intending to use, one of the many
competing public telecom operators (PTOs). If CLI is important to you, then you should be
aware that CLI (when used for display purposes) is an optional service and PTOs are not
obliged to provide it. You should therefore ask any potential PTO provider whether, and
what, CLI services are supported.
ISDN and mobile networks
2.4
Calls between compatible ISDN equipment have been able to transfer CLI numbers
even before similar services were launched for the residential consumer in 1994. As such
they should conform to ISDN standards. In some cases, ISDN systems may not be able to
make the distinction between CLI being unavailable or being withheld and you should bear
this in mind when receiving calls over such systems. The new Euro-standard ISDN does
support the distinction. However, in most cases, originating ISDN lines can use both 141 and
the standard ISDN blocking code (1471) to withhold the number. ISDN standards refer to
the display of CLI as CLI Presentation (CLIP) and the blocking service as CLI Restriction
(CLIR).
2.5
CLI on digital mobile networks such as GSM 900 and 1800 works in a similar way to
ISDN.
Presentation Numbers
2.6
In order to explain some of the CLI options in greater detail, it is useful to appreciate
how CLI is generated and transmitted across public networks. There are two forms of CLI.
Firstly, there is the Network Number (NN) which is set by the public telecom operator (PTO)
and usually corresponds to the regular directory number of your line. Secondly, there is the
Presentation Number (PN) which may either be set by the PTO or by your own terminating
equipment to be a number on which you wish to receive return calls, if for some reason it is
not possible or desirable to have return calls to the Network Number.
2.7
There are three types of PNs. Type 1 is applied to your outgoing calls by the PTO at
the local exchange. Type 2 PNs use the direct-dialling in (DDI) number of an extension
sitting behind a PABX. Type 3 PNs may be used in circumstances where the 'far end
breakout' problem described below arises and involve a customer's own equipment applying
the CLI number to a call.
2.8
If you wish to use a Presentation Number, you should contact your PTO about this. If
the PN you want to use does not correspond to a line which is rented by the same person or
company you will need the written authorisation of the person or company to whom that
number has been allocated.. The number may not be a premium rate information number, but
all other numbers are allowed as long as they are diallable. There are several reasons why you
might want a PN. For example, your lines may be ‘outgoing only’ and you wish return calls
to go elsewhere. Alternatively, you wish all return calls from a group of lines to go to one
enquiry number. If the PN corresponds to a line which belongs to another PTO, the PTOs
will liaise to ensure that the PN is valid and is in either your name or that of someone who has
authorised your use of it..
2.9
Both NN and PN are carried across the network as calls are set up, including calls
which pass to other PTOs. At the distant exchange, customers using Caller Display or Call
Return are sent the PN, if one is available, otherwise the NN is sent. Note, however, that
there are a few PTOs that cannot handle PNs . If you use a PN, you should advise your PTO
whether you would prefer, in such circumstances, for your NN to be sent, or the CLI shown as
‘unavailable’. This preference would only apply where the distant PTO cannot handle PNs,
in all other cases, the normal PN would be made available.
CLI on PABX systems
2.10 If you have a PABX with Direct Dialling In (DDI), you will need to consider carefully
how you use CLI. Where you connect to the PTO with a digital line (usually one capable of
carrying ISDN), it will usually be possible for you to transmit the number of the calling
extension to the PTO. This is known as a type 2 PN. and the PTO will transmit a PN
comprised of the known number stem of your PABX with the extension number suffixed to
it. The NN will usually continue to be set to the switchboard number. Thus customers you
call should be able to see or access the number of the actual extension which made the call
and return calls to it. This avoids return calls to the switchboard operator who will in general
be unaware of who might have called a particular customer. It is also useful to prevent an
increase in calls to the switchboard, as you might have to employ more operators.
2.11 With this system of CLI, the PTO will verify that the extension number you send is a
valid one within the agreed range. In this way, customers can remain assured that the CLI is
authentic.
2.12 If you have a network of PABXs, you may be using a feature usually known as ‘far
end breakout’. This is a way of routing your outgoing calls to the public network, where the
call routes first to one of your distant PABXs before connecting with the PTO, in order to
take advantage of local charge rates from that point. In this instance, the second PABX will
not be able to send forward the extension number of the calling extension, even if it is known.
This is because the extension number would not correspond to the number stem stored by the
PTO as the Partial CLI. Because of this problem, many customers with such private networks
have chosen to withhold their CLI permanently, rather than allowing the default switchboard
number to be seen by the called customer.
2.13 To overcome this problem, especially as Anonymous Call Rejection becomes more
common OFTEL has decided to allow large private networks to transmit complete PNs,
rather than the present system of sending only the extension number. Such numbers are
known as type 3 PNs. To counterbalance any risk to the reliability of type 3 PNs stringent
checks are applied before a customer is permitted to use them with OFTEL having the final
say.
Indirect Access to other PTOs
2.14 You may subscribe to the services of an alternative PTO, usually to make use of long
distance or international services. In some instances, you dial a short code or an 0800
number, or press a special phone button and are then invited to identify yourself to the second
PTO using your touch-tone keypad, before entering the wanted number. This is called twostage call set-up. When you use two-stage call set-up, the second PTO will not necessarily be
aware of your privacy preference, that is, whether you have dialled 141 or have your CLI
permanently blocked.
2.15 In most instances, it is now possible to dial a short access code (eg 1XXX)
immediately followed by the desired number. This is called one-stage call set-up. In these
cases, the second PTO identifies who is calling by using the Network Number CLI and this
allows the PTO to bill you correctly for the call. This has a number of implications you
should be aware of.
2.16 Firstly, you may withhold your number by dialling 141, as usual, if you don’t want
your number to be available to the called customer. It is essential that the 141 digits are
dialled before the indirect access code. The second PTO will still have access to the NN for
billing purposes. It is worth checking with your chosen indirect access operator that their
system will respond to the 141 prefix as some do not. In these cases your CLI will always be
treated as if it were 'unavailable'.
2.17 Secondly, you may not access your PTO from a telephone line different from your
normal one, as the CLI will not correspond to the one recognised by the second PTO. If you
need to make calls from varying lines, ask your PTO about Calling Card services.
2.18 Lastly, if you use Call Diversion, it is unfortunately not possible to divert calls using
your second PTO’s indirect access service. This is because, on a call which has been diverted,
the CLI sent forward on the diverted leg of the call is that of the original caller whose call has
been diverted, and not yours. Thus the indirect access PTO will not recognise the CLI as a
valid number for your account. The reason why CLI works this way, is to prevent callers
being able to send a false CLI number by diverting via a third party. It is important that the
CLI accessible to customers always represents a diallable number to which return calls can be
made to the caller.
Adaptors
2.19 You may be making use of indirect access PTO services by means of an adaptor,
sometimes known as an autodialler, between your system and the public network. This is
programmed to route calls to the alternative PTO by inserting the appropriate indirect access
code. You should be aware that some adaptors route all calls beginning with the digit 1 to the
regular directly connected network (usually BT). Thus if you withhold CLI using 141, the
call will default to BT. If you need to withhold CLI on a majority of your calls, it would be
best to have your line permanently blocked for CLI and use 1470 when you wish to release
CLI. (Of course 1470 calls would also default to BT). Again you are advised to check with
your indirect access operator whetrher this applies in your case.
Carrier preselection
2.20 From December 2000 if you are a BT customer you can select other providers over
your existing line without having to dial extra digits or use an adaptor. This is called "Carrier
Pre-selection" (CPS). Initially CPS will be available for national and international calls only,
with an "all calls" package added about a year later. After you confirm that you wish to use
another supplier for specified call types, your choice will be applied to every call until you
choose otherwise. You will also be able to combine one- or two-stage indirect access
services with CPS, by over-riding your CPS selection on a call-by-call basis.
2.21 If you wish to withhold your CLI - whether for every call via a permanent block on
their CLI, or for individual calls by dialling 141 before the number - will still be able to do
this if you have CPS.
Call Centres
2.22 Many Call Centres operate within the UK, and often use the received CLI, via
Computer-Telephony Integration (CTI) systems to alert the call centre operator to who is
calling and, where the customer is already a known contact, to bring up stored information
from a computer to assist with the handling of the call. This is an acceptable use of CLI, but
in other circumstances, captured CLI numbers may not be used for more general marketing
purposes, such as compiling target lists for an outbound calling programme. Annex A gives
further information from what was then the Data Protection Registrar about acceptable uses
of captured CLI.
Service Providers
2.23 As mentioned above, the PTOs transfer CLI (both NN and PN) between themselves,
irrespective of whether you have requested it to be withheld from those you call. This is
necessary for a range of reasons, including billing, call tracing and the handling of operator
and 999 calls. To ensure that your privacy preferences are maintained, all PTOs are bound by
a Code of Practice, backed up by their interconnect contracts, to ensure the authenticity and
integrity of CLI and its privacy indicators, be it ‘withheld’ or ‘unavailable’.
2.24 Independent (non-PTO) Service Providers connecting to PTO networks cannot access
any CLI if the caller has withheld it. In some cases, it is important for Service Providers to
have access to such CLI for management and billing purposes or if it needs to be passed on to
another PTO for final call delivery. Internet Service Providers (ISPs) also require CLI
information for traceability purposes, ie to discover the source of illegal material posted on a
website. In order for Service Providers to be able to see the CLI as PTOs do now, they need
to be subject to binding contracts concerning the maintenance of privacy and integrity of the
CLI information. They also need to comply with a Code of Practice for Service Providers,
imposing similar obligations to those contained in the existing Code of Practice for network
operators, that is expected to be published this year.
The CLI Interest Group
2.25 If you have an interest in debating and assisting future policy for CLI services, you
may wish to join the CLI Interest Group. This is open to all industry members, consumers
and their respective representative organisations. It is facilitated and chaired by OFTEL. For
further information, contact Frank Phillips on 020 7634 8871.
Glossary of terms used
anonymous call rejection (ACR): a service which prevents calls from being connected or
put through where a caller has withheld CLI
block blocking: same as ACR, the blocking of calls where the caller has blocked or withheld
CLI
call return: a service which enables a call to be returned to the line from which the last
incoming call was made
caller display: a subscription service which displays the number from which a call has been
made - it requires a caller display unit with a screen, either on the telephone or as a separate
attachment
carrier preselection (CPS): a service which enables a customer to select an alternative
telecommunications service provider without having to dial extra digits or use an adaptor
computer telephony integration (CTI): the integration of screen-based computer functions
with telephony
direct dialling in (DDI); a switchboard’s capability to route an incoming call to the
extension dialled, without the intervention of an operator
ISDN: Integrated Services Digital Network - the most widely available digital network,
providing a wider range of services than an analogue network can support
GSM: Global System for Mobile Communications - a digital mobile communications system
operating around the 900 MHz frequency band
line blocking: a service which enables a caller to withhold CLI on all outgoing calls
network number (NN): a number allocated by a telephone company which identifies the line
from which a call has been made, usually the same as the directory number
PABX: Private Automatic Branch Exchange - often described as a switchboard and switches
calls between exchange lines and extensions
PCN: Personal Communications Networks - a digital mobile communications system
operating around the 1800 MHz frequency band, also known as DCS and GSM 1800
presentation number (PN): a number chosen by a caller to which return calls may be made
Telephone Preference Scheme (TPS): a scheme established under the
Telecommunications Data Protection Directive which enables subscribers to register their
wish not to receive any telemarketing calls with a statutory body, the Telephone Preference
Scheme
ANNEX A
THE DATA PROTECTION REGISTRAR
Using the law to protect your information
Calling Line Identification (CLI)
Caller Display - Use of Captured Data
1.
By Caller Display we mean the facility which provides for the display and possible
capture of the caller's number by the called party.
2.
In the implementation of Caller Display concerns about protecting the privacy of the
caller have been recognised and the caller is able to suppress the display of his number
on a call-by-call basis by dialling the prefix 141. Suppression is possible for all calls
made from a particular number.
3.
Caller Display allows not only the display but the capture of the caller’s telephone
number by the called party. If that number is subsequently held as personal data by the
called party, the question arises: has it been obtained fairly?
4.
It is a requirement of the First Data Protection Principle that information to be contained
in personal data is obtained fairly. The Registrar’s view is that this means that the source
of the information should know who is to use the data and for what purpose or purposes
the data are to be used or disclosed. If these matters are not obvious because of the
nature of the transaction, they must be explained to the source before the information is
given. This view has been supported by the Data Protection Tribunal in its decision
regarding Innovations (Mail Order) Limited.
5.
There are a number of reasons why the calling number might be retained by the called
party. These range from use by a private subscriber simply to return the call, to
commercial use such as enhancing an existing customer database or establishing a new
database.
6.
The Registrar would accept that use of the captured number in direct connection with the
original call by the called party is a use which the caller would reasonably expect. Such
use could include the example above of returning a call if the called party had been
unable to take the original call immediately. (in any event, in this case it is arguable that
the information retained is not personal data). Another such use, in a commercial
context, would be to reference an existing customer database if the number were already
held on it.
7.
However, the Registrar considers that obtaining the number and holding it as personal
data if it were not already held as such is something which may not be obvious to the
caller. In those circumstances, it is likely that the fair obtaining requirement of the First
Principle would have been contravened by the called party if no explanation had been
given to the caller.
8.
A further concern is that individuals may not often ring companies from home.
Therefore, it is dangerous to assume that you can call a specific individual back on the
number from which they have made a call. Where a company wishes to use the number
displayed to get back to a caller a sensible, practical safeguard is to ask a caller if you can
call them back on the number displayed.
"Do you mind if we call you back on 020 7634 8871?" (or whatever the number
displayed is).
9.
10.
It is easy to envisage circumstances in which the calling number could be retained for
purposes which are unconnected with the original call. An example would be to enhance
a marketing database which is intended to be rented to other companies for their
marketing purposes. The Registrar considers that to retain the number for such purposes
without the express consent of the caller, would be likely to contravene the First Data
Protection Principle.
In summary, the essence of the matter is that the callers number may only be captured
and held as personal data by the called party for purposes directly connected with the
original call, unless the caller gives express consent to its subsequent use for other
purposes.
Data Protection Registrar
14 August 1997
[CLIguideV2050200.doc]