Methods of this kind are used in environments, in which there are several users of a subscriber connection of a telephone network. These methods are used when it is wished to route a call to the subscriber connection in such a way that the desired respondent, and no-one else, answers the call.

One method according to the state of the art for assigning to a desired respondent a call made to a subscriber connection being examined can be implemented by means of a 'specified call'defined in national subscriber operations. This function permits user- specific coded ringing to be sent in connection with a call-connection request sent to the receiving subscriber connection, so that the correct person can answer the telephone on the basis of the coded ringing. In such solutions, the local switching centre of the receiving connection can use multiple subscriber numbering or re-dialling to send the desired coded ringing to the receiving connection..

The state of the art has the drawback that it has no effective way to restrict the possibility of an unauthorized person in the vicinity of a terminal device connected to the subscriber connection being examined from answering an incoming call. This is a problem when it is wished to conceal the identity of the calling subscriber from at least some people in the vicinity of the subscriber connection. Another problem with a call made to a respondent assigned by user-specific coded ringing is that only four subscriber numbers per connection are available to define the user-specific coded ringing, which is not enough for all operating requirements.

The invention is intended to eliminate the defects of the state of the art disclosed above and for this purpose create an entirely new type of method for assigning to a desired respondent a call-connection request directed to a subscriber connection.

The invention is based on using an intelligent network switching centre to assign a call- connection request, directed to a subscriber connection, to a desired respondent and using the control of the intelligent network switching centre to supervise that the call is answered by a respondent using the identifier data issued to the desired respondent.

More specifically, the method according to the invention is characterized by what is stated in the characterizing section of Claim 1.

Considerable advantages are gained with the aid of the invention. The use of PSTN subscriber connections becomes appropriate in conditions in which this was previously not the case. The invention effectively restricts the possibility that an incoming call may be answered by an unauthorized person in the vicinity of a terminal device connected to the subscriber connection being examined. This is advantageous in situations in which it is wished to conceal the identity of the calling subscriber from at least some people in the vicinity of the subscriber connection. Such a situation is one in which people live together and use a common telephone. The invention permits a specific telephone or telephone connection to be jointly owned but privately used. A mobile telephone can also be operated according to the invention.

In the following, the invention is examined with the aid of an example and with reference to the accompanying drawings.

Figure 1 shows one apparatus for implementing the method according to the invention.

The flow chart of Figure 2 is divided into parts 2a and 2b on two pages and shows one method according to the invention for assigning to a desired respondent a call- connection request directed to a subscriber connection, with the aid of an SCP of the telephone network, an IP notification device and the other apparatus shown in Figure 1.

The apparatus according to Figure 1 is as follows: Calling connection 11 is the calling connection, the identity of the person calling from which it is wished to conceal from people in the vicinity of called connection 15, who do not know the valid password.

SSP centre 12 is any SSP-level switching centre, which can perform IN triggering on the basis of a called-subscriber identity received from the calling connection.

SCP 13 is an intelligent-network controller, to which SSP centre 12 can perform IN triggering.

IP notification device 14 is a device able to send a desired message to a telephone connection connected to a specific subscriber connection.

Called connection 15 is a subscriber connection, to which a call-connection request is assigned according to a specific subscriber identity, referred to here as the called subscriber identity, received from the calling connection. There are several called subscriber identities corresponding to a single called connection 15, each being set to respond to the identifier data of its own user. In the method according to the invention, such user identity data must be received from called connection 15, as a condition to form a telephone connection between calling connection 11 and called connection 15.

The following is a more detailed description of the operations shown in the flow chart of Figure 2: Typically, notifications are only sent from the IP device to the calling subscriber. In the method according to this example, ICA calls (Initiate Call Attempt) are used to send notifications from the IP terminal device to the called subscriber. Such an ICA call is a so-called temporary call made by the initiating intelligent network controller SCP, by an ICA operation belonging to the IN standards. The individually numbered points in the flow chart of Figure 2 refer to the following: Points 101-102 of the flow chart are performed to notify the intelligent network of the wish, expressed by the received number dialling, of calling connection 11 to be in telephone connection with a respondent according to a specific called subscriber identity, such as the called subscriber number.

101) A call-connection request, such as a dialled number, is received at SSP centre 12 from the direction of calling connection 11.

102) Data on the call-connection request received from the direction of calling connection 11 is transmitted from SSP centre 12 to intelligent network controller SCP 13 (Service Control Point).

Stage 103 of the flow chart is performed, to ascertain if a definition according to the received called subscriber identity is obtainable from SCP 13. If such a definition is not obtainable from SCP 13 at the relevant moment, stages 104-105 of the flow chart are carried out. Otherwise, the procedure continues from point 106 on.

103) An IN script, set to be performed in response to a specific call-connection request received in SSP centre 12, is started.

104) If the received called subscriber identity cannot be successfully entered in the script, calling connection 11 is notified that the call has failed.

105) After this, the call is broken.

Stage 106 of the flow chart is performed, to ascertain if a bound called connection identity according to the received called subscriber identity is available to SCP 13. If such a connection identity is not available to SCP 13 at the relevant moment, stages 108 -109 of the flow chart, or other operations bound to the called subscriber identity are performed. Otherwise, after point 107, the procedure continues from point 110 on.

106) If the called subscriber identity is entered in the script, it is used to retrieve the called connection identity, such as the called connection number, from the subscriber data, for use here as a control-technical destination identity, such as a control-technical destination number.

107) The data bound to the called subscriber identity according to the IN script is checked in the control of SCP 13.

108) If a called connection identity bound to the received called subscriber identity is not found in the subscriber data, calling connection 11 is notified of the fact.

109) After this, the call is broken.

Points 110-112 of the flow chart are performed to send the desired notification from the IP notification device to called connection 15 and points 113-121 are performed, to ensure that the call being formed is only assigned to the desired respondent.

110) The IN script starts to form an ICA call to the connection, called connection 15, according to the called connection identity found in the subscriber data, and sends it a call-connection request.

111) In response to the off-hook signal received from called connection 15, the intelligent network is commanded to form a temporary call connection between IP notification device 14 and called connection 15.

112) IP notification device 14 notifies called connection 15 of the person to whom the call is coming while also requesting called connection 15 for either a password, or else a signal or message signifying that the desired respondent is not present.

113) A password attempt expressed in DTMF characters is received from the direction of calling connection 15.

114) The received password attempt is examined for a signal or message signifying that the desired respondent, in this case the specific called subscriber, is not present.

If a signal or message signifying that the desired called subscriber is not present, is received at point 114, the procedure continues from point 115. Otherwise it jumps to point 117.

115) Calling connection 11 is notified that the desired called subscriber is not present.

116) After this, the call is broken.

117) The received password attempt is compared with the password defined in the subscriber data of the desired called subscriber.

If the received password attempt does not correspond to the password defined in the subscriber data of the called subscriber, points 118-119 of the flow chart are

performed, otherwise a telephone connection is formed between calling connection 11 and called connection 15, as described in points 120-121.

118) Calling connection 11 is notified of the received wrong password attempt.

119) The call is broken.

120) If the password defined in the called subscriber's subscriber data corresponds to the received password attempt, the ICA call formed in point 110 is broken.

121) A telephone connection is formed between calling connection 11 and called connection 15.

Thus, a telephone connection between calling connection 11 and called connection 15 is formed with the aid of IP notification device 14 and SCP 13.

The invention can also be applied in the ways disclosed below: As in a specified call, called subscriber numbers can be effected by either re-dialling or multiple subscriber numbering. If the call is made by re-dialling, an extra number is added after the connection's call number. In multiple subscriber numbering, any number at all leading to IN triggering can be chosen from the unallocated number space as the call number.

When the message is sent from the notification device to the person answering the call, the message can be given either as the connection number or, for example, as the name of the owner of the connection number. The latter requires a great many names to be recorded in the IP device.

If the called connection gives the'connection owner not present'sign, e. g. (#), then, as shown on the flow chart, the calling subscriber is notified that the owner is not present and the call is broken. Alternatively, this can be done by not breaking the call, but allowing the calling subscriber to either break the call or call the normal telephone number of the called connection. If the calling subscriber chooses the normal number, the call is formed with the aid of the IP device, just like an ordinary call.

The invention can also be applied in mobile telephones. In some cases, a single mobile phone can be used by several people.

The password checking shown in the flow chart can take place in such a way that a password can be given, for instance, three times before the call is broken.

If the network elements wait for a password chosen by the called subscriber, it is best to set a time limit, within which the call is broken unless the called subscriber chooses a password.

The method according to the invention uses a subscriber connection connected to a telecommunications network to receive user-definable control data, such as DTMF audio frequency signals. A call-connection request refers to telecommunications network control signalling used to request the devices of a telecommunications network, or devices connected to a telecommunications network, to open a specific data transmission channel. A call-connection request can be assigned to a desired respondent in the vicinity of the subscriber connection, such as a person, a group of people, an identity relating to a person's particular function, or even a device, an application program operating though a device, or some instance of such a program.

A respondent's individuation data refers to the respondent's subscriber identifier, such as the called subscriber number, which is connected to a telecommunications network to refer to the called connection being examined. The respondent's identification data, which is a data record available to the intelligent network, is attached to the respondent's individuation data. Thus, the respondent's individual data and the respondent's identification data form a response pair in the telecommunications network, for instance, in a specific database available to the SCP.

The subscriber connection is notified of the respondent to whom it is wished to connect the call by being sent an assigning message. Examples of such an assigning message include notification sent by the IP notification device to the subscriber connection or a text message sent to the switching centre's ISDN connection.

An identification data attempt is control data, definable by the respondent, received from the subscriber connection, which the telecommunications network is set to

compare with specific respondent individuation data concerning the respondent, to whom it is desired to assign the call-connection request. In this application, an identification data attempt and a password attempt mean the same as identification data and a password.

An identification data attempt is compared with the individuation data of a specific respondent in the telecommunications network and/or in the control of the telecommunications network in such a way, for example, that the SCP or some other intelligent network element controls the making of the comparison. An intelligent network is a telephone network sub-system, or a system with a telecommunications connection to a telephone network, set to control the more complex call-control operations.

A notification device is a separate system or the sub-system of a switching centre, from which the switching centre receives information that it can transmit to a data transmission channel formed to the subscriber connection using a switched connection.