Mechanism to control telecommunication connections in a digital switching network

Disclosed is a mechanism to control telecommunication connections via digital switching networks like the ISDN. Frequently observed scenarios are a caller who is connected to an answering machine, although he intended to talk to a human individual, or where a node is shared by more than one individual and the caller wants to talk to a definite person likewise. Subscriber information is interchanged between a calling device and a called device before setting up the connection which is utilized to inform the caller about the device type at the called side or to inform the called side about the desired person. In the ISDN, a called device sends an ALERTING message to a switching center before accepting the connection. The switching center forwards a part of that message to the calling device which includes the so-called USER--USER Information Element (UUIE). In that USER--USER IE, an information like "UNDER THE CALLED NUMBER AN ANSWERING MACHINE IS BECOMING ACTIVE" can be coded. The USER--USER IE is transmitted by the ISDN network transparently to the calling device and thus can be presented to the calling participant via a display device. Alternatively, a different dial tone can be generated by the calling device to inform the participant about the answering machine.

BACKGROUND OF THE INVENTION
 1. Field of the Invention
 The invention pertains to a method and a device for controlling
 telecommunication connections via digital switching networks, in
 particular for telephone connections between participants of a telephone
 network like the integrated-services digital network (ISDN).
 2. Prior Art
 A frequently observed scenario of telecommunication via switching networks
 is that a caller is connected to an answering machine, although he
 intended to talk directly to a human individual. So the caller hangs up
 and pays for a not desired telephone connection. Currently every time
 telephone participants talk to an answering machine they have to pay
 telephone charges and waste time.
 Another typical scenario in the field of telephone communication is where a
 node is shared by more than one individual and that a caller wants to talk
 to a definite person who currently is not present. Thus, another person
 will take the call, accordingly causing costs and time.
 A first prior art approach for preventing non-desired telephone calls is an
 automatic telephone answering machine, disclosed in Japanese Patent
 Publication JP 60-229561, assigned to NEC Corporation and entitled
 "Automatic Telephone Answering Device". Its purpose is that the answering
 device automatically calls a called subscriber only when a calling
 subscriber voices a specific word, but does not answer to a silent
 telephone call. Proposed is a responding message sender controlled by the
 output of a voice detector which detects the specific speech of the
 calling subscriber and sends out a control signal to a speech answering
 circuit and a calling circuit. Both circuits are activated and the speech
 answering device sends out an answer message to the calling subscriber and
 also transmits a tone to let the subscriber know of the incoming call.
 A second known approach, a responder absence indicating system for
 telephone sets, is disclosed in Japanese Patent Publication JP 59-122066,
 assigned to NEC Corporation and entitled "Display System for Absence of
 Responsor from Telephone Set". Proposed is to store an absent status by
 identifying a dial number of a registered absent status. The objective is
 to allow an originating subscriber to confirm absence of a responsor by
 storing presence or absence of the responsor regarding every telephone
 set. It is particularly proposed to discriminate and display a dial number
 for absence registration from a telephone set. A controller receives a
 dial number of a telephone set and sends it to a discriminating circuit
 which discriminated the number to store the absence state in the address
 of said telephone set. When a second telephone set originates to the first
 telephone set, a tone is sent out and the absence of the responsor from
 the first telephone set is confirmed.
 There exist further approaches which let a called subscriber know who
 calls, to identify a caller before answering. In a respective system
 disclosed in Japanese Patent JP 1243757, assigned to Toshiba KK, the ISDN
 subaddress information is utilized for that purpose.
 A similar approach for identifying a calling terminal is subject matter of
 European Patent Application 0 680 239, assigned to Nippon Telegraph and
 Sharp KK. There, a connecting facility connects calls from an identified
 calling terminal to a private ISDN terminal. A switching system has an
 identifier unit which identifies the calling terminal of an incoming call
 by a calling number and a subaddress in a call-setting message. Finally,
 an approach for improving communication effectiveness and efficiency by
 excluding unnecessary connections of terminals is disclosed in Japanese
 Patent JP 7123170, assigned to Nippon Telegraph, where an incoming call
 from a terminal to another terminal, which are interconnected via ISDN, is
 notified to a user through a display unit. An address circuit hereby sends
 a predefined specific code to a substitute address information element at
 the time of transmission of the call. An address checking circuit checks
 whether the address is available in the incoming call signal. If the
 address is not available in the calling signal, a control circuit
 identifies it as standard communication mode and notifies this to the user
 through the display unit.
 SUMMARY OF THE INVENTION
 The known approaches do not solve the problem underlying the present
 invention, namely to provide a method to avoid being connected to an
 answering machine when a participant only wants to talk to a human at the
 other side, or to a definite person, respectively.
 The invention solves the above problem by interchanging participant
 information between the calling device and the called device, before
 setting up the connection. That information can be utilized to inform the
 caller about the device type at the called side or to inform the called
 side about the desired individual which the caller wants to talk with.
 Hereby, the caller or the called individual, respectively, can decide to
 accept a connection or not to accept.
 A first application scenario is a situation where a human caller wants to
 get a telephone connection to another human participant, wherein an
 answering device is provided on the called side, too. A second scenario is
 a situation where a human caller wants to talk with a definite person and
 wants to avoid costs for a connection with an undesired person. For
 instance, he wants to talk with a person which is not present where
 typically another person receives the call instead of the intended person.
 The proposed function is different from known approaches insofar as it does
 not provide an indication of the calling number to the called participant.
 In contrast to those approaches, according to the concept of the
 invention, the calling participant provided specific information about the
 desired called participant. It is further emphasized that the present
 invention is applicable to common telephone calls, telephone and video
 conferences, including device--device connections, human--human
 connections, and mixed connections between devices and human participants.
 By use of, for instance, a different alerting tone or a display message, a
 caller can be informed that e.g. an answering machine is active at the
 called participant's side. This information can be provided by the
 answering machine and transmitted via the known ISDN ALERT message. The
 ISDN ALERT message is part of the actual ISDN protocol definition.
 Thus, the proposed method saves caller's time and money and thereupon
 increases network performance by reducing the amount of unintended
 connections and keeping the network free for other intended connections.
 An information that an answering machine is active under a called telephone
 number is not known in current switching networks. For that reason, the
 called device, e.g. the answering machine itself, has to notify its device
 type to the calling device, e.g. a telephone. Exchange of such information
 before setup of an operable connection is already supported in digital
 switching networks like ISDN, in contrast to analog switching networks.
 For instance, in ISDN a called device sends an ALERTING message to a
 switching center, before accepting the connection. The switching center
 forwards a part of that message to the calling device which includes the
 so-called USER--USER Information Element (UUIE). The USER--USER
 information element is a block of information comprising information about
 the users. It may be included in known ISDN messages, like in the ISDN
 SETUP message or the ISDN ALERT message. In said UUIE, an information like
 "UNDER THE CALLED NUMBER AN ANSWERING MACHINE IS BECOMING ACTIVE" can be
 coded. In an analogous manner, other information about end devices can be
 coded, like about Telefax or Personal Computers.
 The UUIE is transmitted by the ISDN network transparently to the calling
 device and thus can be presented to the calling participant (person) via a
 display device. Alternatively, a different dial tone can be generated by
 the calling device to inform the participant about the answering machine.
 Hereby, the calling participant can be informed about the called device
 before setting-up (accepting) an active connection (CONNECT), without need
 of any changes in the switching units of the ISDN network.
 Therefore, a particular advantage of the proposed solution is that the
 existing ISDN switching service must not be amended for an implementation
 of the invention.
 In cases of multi-subscriber telephone numbers, a preferred embodiment is a
 smart telephone device which interprets the called party number or the
 calling party number. The corresponding Information Elements (IEs) are
 also provided in the SETUP CONNECTION message. This IEs can be used for
 example, to ring a bell in different tones depending on the called or
 calling individual.

FIG. 1 depicts a situation where a caller is calling a number via an ISDN
 digital switching network, wherein at the called side an answering machine
 is currently active. It is particularly assumed that the caller does not
 intend to talk to the answering machine, but only to the respective
 subscriber (individual) registered for that telephone number.
 At first, a connection setup is initialized by the caller wherein a setup
 message is transmitted to the called side via the ISDN network. The
 end-device at the called side returns an ALERTING message before accepting
 a connection. The ISDN network then forwards a part of that message to the
 calling device which includes a so-called USER-to-USER Information Element
 (UUIE). In that UUIE, an information like "UNDER THE CALLED NUMBER AN
 ANSWERING MACHINE IS BECOMING ACTIVE" can be coded by setting a predefined
 value. Since there is no such value defined yet, it has to be agreed on by
 end enjoyment supplier committees.
 The UUIE transmitted over the ISDN network is received at the calling
 device and thus can be presented to the calling subscriber (person) via,
 for example, a display device. Alternatively, a different dial tone can be
 generated by the calling device to inform the participant about the
 answering machine currently being active.
 The internal logic required for generating the UUIE will be described,
 together with the steps performed by said logic, according to the left
 half of FIG. 4. This logic has to be included in the answering machine
 (ANSWERING MACHINE LOGIC). The following steps are performed: First, the
 ISDN SETUP message is received (INCOMING SETUP) by the answering machine
 from the ISDN network, according to FIG. 1. Next, a UUIE indicating that
 only an answering machine will respond has to be generated. For this
 purpose, extra logic at the answering machine is required. In the left
 half of FIG. 4, this extra logic is depicted as a box (SET UUIE=ANSWERING
 MACHINE). Next, the ISDN ALERTING (UUIE) message according to FIG. 1 has
 to be generated, with the UUIE being included in said message. Said ISDN
 ALERTING (UUIE) message is retransmitted to the ISDN network (OUTGOING
 ALERTING).
 In another scenario where a caller cannot reach a desired person since that
 person not being present, e.g. out of the room, whereby another person is
 authorized to accept calls at the respective end-device, the according
 ISDN protocol is shown in FIG. 2. In contrast to the case of FIG. 1, an
 UUIE is transmitted to the called side (callee) via the setup message. The
 UUIE contains information about the desired callee. This information can
 be put in by the caller using a alphanumeric Keyboard (e.g., the callee's
 name) or special key combinations before setting up the call. With this,
 different participants can be assigned to the same telephone number and
 called by using different function keys.
 The called device, if capable to process this information, can easily show
 the callee's name on a display. In addition it could also ring using a
 prefigured tone. For this, it is mandatory for the calling and called
 device to use the same semantic of the UUIE information exchanged.
 With regard to an implementation of the proposed functionality by
 utilization of the existing ISDN transmission protocol, various
 embodiments are possible. By use of an end-device selection number, the
 so-called "Endgerate-Auswahlziffer" (EAZ), different end-devices can be
 operated at the same (telephone) line. Thereupon, an end-device can be
 assigned to multiple EAZ numbers which are used by the end-device for
 selection of a particular dial tone or a displayed information. It is
 noteworthy that in the new European (Euro-)ISDN Standard DSS 1 of the
 European Telecommunication Standards Institute (ETSI), the EAZ is not
 provided any longer. Instead of EAZ, a so-called "Multiple Subscriber
 Number" (MSN) can be used for the same purpose.
 In an analogous manner, the ISDN subaddress enables the selection of
 different participants using the same end-device. Alternatively, to the
 approach described above using UUIE the subaddress can be used to address
 different participants and initiate the same logic, e.g. using different
 bell tones. Common to both approaches is to have the same understanding on
 both sides about the UUIE or subaddress infonnation respectively.
 FIG. 3 depicts a preferred embodiment of the invention where the proposed
 ISDN functionality for the calling side is implemented into a smart
 telephone device. That embodiment is now described in a situation where at
 the called side an answering machine is active. The telephone device
 comprises a control unit to interpret incoming USER-to-USER information
 (UUI) and to control the hardware components of the telephone device
 accordingly. The UUI can cause a common loudspeaker of the telephone set
 to deliver an acoustic message that at the calling side an answering
 machine is currently active. Alternatively, on a common display of the
 telephone set, a respective written message can be displayed.
 In case of a scenario where a definite subscriber is desired, the
 respective information of that person can be input into the control unit
 via an alphanumerical keyboard of the telephone device. The respective
 control unit of the telephone device on the called side, in a preferred
 embodiment, controls a common display where the name of the desired
 subscriber is viewed. Thus, in case of the desired person currently not
 being present, other persons which are also authorized to take calls from
 that device, are invited not to accept the call.
 An exemplary embodiment of the smart telephone device's control unit at the
 calling side, and the steps performed by said control unit, are described
 with reference to the right half of FIG. 4 (SMART TELEPHONE DEVICE LOGIC).
 The following steps are performed: First, the ISDN ALERTING (UUIE) message
 is received (INCOMING ALERTING), from the ISDN network, by the smart
 telephone device. This corresponds to the caller's side at the left of
 FIG.
 In the smart telephone device, additional logic for analyzing an UUIE which
 might be contained in said ISDN ALERTING (UUIE) message has to be
 provided. Said additional logic first checks whether an UUIE is present or
 not (UUIE=PRESENT ?). In case there is no UUIE present, the tone the
 caller hears is the normal tone. In the right half of FIG. 4, the circuit
 that produces said normal tone is depicted as a box (USE NORMAL TONE).
 In case there is an UUIE present, another logic has to check whether said
 UUIE indicates an answering machine at the number being called
 (UUIE=ANSWERING MACHINE ?). In case there is no answering machine, the
 tone the caller hears is the normal tone, which is generated by the
 corresponding circuit (USE NORMAL TONE). In case there is an answering
 machine at the other end, the tone changes: A special tone is generated by
 activating the USE SPECIAL TONE circuit of the right half of FIG. 4. This
 concludes the description of the present invention.
 While the invention has been particularly shown and described with
 reference to preferred embodiments thereof, it will be understood by those
 skilled in the art that various changes in form and details may be made
 therein without departing from the spirit and scope of the invention.