Description of the Related Art Telephone communication has become ubiquitous since its inception in the late l9th century. The first local exchanges wired a number of homes to a central switchboard, where a human operator stood by to complete the connection between a caller and the party being called. Soon, local exchanges were connecte to each other, giving a caller access to correspondents far outside the local area. Later, transcontinental and even transoceanic cables made phone access to almost any area of the world possible.

Just as telephony's geographical reach extended, so too did its impact on our daily life. Business could be conducted, relatives kept in touch with, and information obtained simply by dialing a telephone. The ability to converse with someone else as if they were in the same room was an enormous improvement over existing mail and telegraph services. So beneficial were telephone's avantages that initiatives were launched by the government of the United States and other countries to ensure that their entire population had access to this form of communication.

Once telephones pushed beyond their most rudimentary installations, the rapidly increasing number of users compelled the use of better identification, that is, telephone numbers. Automatic switching centers could route telephone calls to distant exchanges based on the series of numbers dialed, or later entered via push-buttons, by a telephone caller. The use of directory numbers lessened the need for relance on human operators, and eventually proved to be more convenient and reliable.

As the number of telephone users grew, so did the length of telephone directory numbers. In the U. S., for example, where four-digit numbers once sufficed, seven-

digit numbers eventually became the standard. And even though many telephone service subscribers can be uniquely identifie with numbers of this length, it is now frequently necessary to first dial an area code. Unfortunately, area codes are now becoming independent of geographic areas, creating for all practical purposes ten-digit telephone directory numbers.

In addition, telephones are no longer limited to voice transmission between homes or businesses. Their use has been adapted to transmitting electronic pages, data, facsimiles, and cellular mobile calls. These new services, combine with the ever-growing number of traditional phone service subscribers, has begun to rapidly deplete the supply of available directory numbers.

Further use of directory numbers has been dedicated to serving subscribers who wish to have multiple telephone lines for use by different family members. In the home, this means that the same equipment serves to receive calls directe at different people. Or the modem home may have a number for personal use and one for business. Even where the same equipment is shared, however, calls for different users or purposes are distinguishable distinctive alerting-a different ring sound or pattern for each. Calls initiated by dialing different directory numbers are in this way routed to a single location but announced in a unique manner, so that the called subscriber knows which number was dialed before answering the phone a making an inquiry.

Notwithstanding its usefulness, however, a distinctive alerting service dependant on the use of multiple telephone directory numbers contributes significantly to their depletion.

One solution to telephone-number depletion has been to effect distinctive alerting simply by adding an extra digit to the dialed telephone number, where the final digit represents one of the alternate users or uses. Each subscriber still needs to be assigne only a single directory number (assuming there are less than ten associated users). This solution is not, however, universally available because it requires a system that uses a variable number length. This service is not available, for example, in World Zone 1, encompassing the U. S., Canada, and the Caribbean.

A method is needed, therefore, to allow multiple users in a single telephone subscription the service of distinctive alerting without the need to deplete the supply by assigning different directory numbers to each user.

SUMMARY OF THE INVENTION To address that foregoing and other problems, the present invention proposes a system and method for facilitating distinctive alerting without using multiple directory numbers. In a preferred embodiment, a telecommunications network dedicates a unique service code for the purpose of invoking distinctive alerting (referred to herein as a Distinctive Alert Service Code, or DASC). Each user associated with a subscriber having distinctive alert service is then assigne a User Code (UC). A party calling a particular user first dials the DASC and then the user's UC. When the call is set up, this distinctive-alert information is received at the local switching office and transmitted to the switching office associated with the called party.

The switching office associated with the called subscriber inclues a distinctive-alert logic device coupled to a ring generator. When the logic device determines that an incoming call invoking distinctive alerting is being set up, it causes the ring generator to generate the particular alert signal associated with the UC extracted from the received call setup message. The alert signal is then transmitted over a line running to the called subscriber's location, where it will cause an alert that is recognizably associated with one of the users. If no recognizable distinctive alert information is received at the local exchange, or if the service is for some other reason unavailable, the standard alert pattern is used.

Regardless of whether standard or distinctive alerting is used, of course, the local exchange associated with the called party generally first determines if the line to the called party is already in use. If the called party subscriber is off-hook but has call- waiting service, then a call-waiting signal is sent. In one embodiment of the present invention, the call-waiting signal transmitted can also be sent in the one of several distinctly-recognizable patterns that is associated with the UC extracted from the call setup information.

In this manner, telephone service subscribers can avail themselves of distinctive alerting without depleting the supply of available directory numbers, and without the need to resort to longer or variable-length numbers.

A more complete appreciation of the present invention and the scope thereof can be obtained from the accompanying drawings which are briefly described below, the following detailed description of the presently-preferred embodiments of the invention, and the appende claims.

BRIEF DESCRIPTION OF THE DRAWINGS A more complete understanding of the method and apparats of the present invention may be obtained by reference to the following detailed description when taken in conjunction with the accompanying drawings, wherein: FIGURE 1 is a block diagram of a telecommunications network according to the present invention; FIGURE 2 is a flow chart illustrating placement of a telephone call according to the present invention.

DETAILED DESCRIPTION OF THE DRAWINGS The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which preferred embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

Reference is now made to FIGURE 1, which is a block diagram illustrating a telecommunications network according to a preferred embodiment of the present invention. The telecommunication network has numerus local exchange switching offices, including a local exchange 10 and second local exchange 20, associated with a calling party 15 and a called party subscriber 25, respectively. Called party 25 is a member of a telecommunications network. The called party 25 has equipment for network access, such as a home or cellular phone, which equipment inclues an

alerting means, such as a ringer 26 or indicator light (not shown). The calling party also has access to the telecommunications network, either as another subscriber, or through temporary facilities, such as a pay phone. Calling party 15 may also be calling from another network through an appropriate gateway (not shown). For the purposes of illustrating this embodiment, it is assumed that called party 25 subscribes to a distinctive alerting service in accordance with the present invention. Further, the calling party 15 is aware the called party 25 has distinctive alert service, and knows an alphanumerical User Code (UC) associated with at least one user. Alternately, the network operator could provide notification to a caller that distinctive alerting is available, or could include in its directory assistance service the UCs of users associated with called party subscriber 25.

Local exchange 10 receives over line 98 a signal that calling party 15 is off hook and, after local exchange 10 responds with a dial tone, it receives the directory number dialed by calling party 15. Local exchange 10 has a Traffic Control System (TCS) 11 that has access to database 12, which contains the routing tables that TCS 11 uses to determine how to efficiently route the call being placed by calling party 15.

The call may be transmitted by a direct connection set up with second local exchange 20 over line 100, or it may pass through one or more intermediate exchanges (not shown).

To set up the connection, TCS 11 generates a call setup signal, for example an Initial Address Message (IAM) 75 according to an Integrated Service Digital Network User Part (ISUP) protocol. The IAM 75 contains the directory number of called party subscriber 25, and is transmitted to second local exchange 20 over line 100 in order to establish a circuit for voice (or other subscriber data) communication. If the call must be routed through intermediate exchanges, then each simply receives the IAM from the proceeding exchange and generates an IAM to transmit to the next (not shown).

To invoke distinctive alerting in accordance with a preferred embodiment of the present invention, the calling party 15, prior to dialing the directory number, first enters a Distinctive Alert Service Code (DASC), followed by the UC corresponding

to the intended respondent. In this event, the DASC and UC are included in the IAM 75 generated by the TCS 11.

Second local exchange 20 inclues a second TCS 30, which is coupled to receive incoming IAM 75 from line 100. Upon receipt, second TCS 30 routes the incoming call to the called party 25 over called-party line 101, based on routing tables maintained on the database 31 associated with second TCS 30. Also associated with TCS 30 is logic device 40, which uses the IAM 75 received by TCS 30 to determine if distinctive alerting has been invoked. If so, logic device 40 accesses database 50, where information concerning particular subscribers is maintained, to determine which distinctive alert pattern corresponds to the UC contained in IAM 75. Ring generator 35, coupled to logic device 40, transmit a signal over line 101 to the ringer 26 of called party 25 to produce an alert in the pattern dictated by logic device 40. In this manner, called party 25 is alerted with a distinctive signal as determined by the UC entered by calling party 15. If no UC was entered, or if for some other reason distinctive alert service is unavailable, then logic device 40 causes ring generator 35 to produce a predetermined standard alert pattern.

Of course, if calling party 15 and called-party 25 are served by the same local exchange, then local exchange 10 and second local exchange 20 are in reality the same switching office, and all operations for distinctive alerting in accordance with the present invention can be handled therein. Although not shown in FIGURE 1, local exchange 10 has a logic device and ring generator that perform the functions of those associated with the second local exchange 20 for calls to subscribers directly connecte with local exchange 10.

Reference is now made to FIGURE 2, which is a flow diagram illustrating the placement of a call in accordance with a preferred embodiment of the present invention.

Local exchange 10 receives an off-hook signal from calling party 15 (step 202), indicating that a call is being initiated. Local exchange 10 responds by returning a dial tone to calling party 15 (step 203). Local exchange 10 then receives, from calling party 15, a DASC, invoking the distinctive alert function and a UC, indicating the specific user that calling party 15 is attempting to reach (step 204). Generally, DASC

entry will be preceded by (or inclue) pressing a distinctive key, such as the * key, signaling the initiation of service code entry. Likewise, the DASC is preferably separated from the UC by the * key. Finally, in this embodiment, the calling party then presses another distinctive key, such as the # key, signaling initiation of directory- number entry. Optionally, the local exchange may then transmit a second or special dial tone, indicating that it is ready to receive further input (step 205). It should be understood that this second dial tone (step 205) may be optional. The local exchange 10 then receives the actual directory number (step 206).

Once local exchange 10 receives all digits input by calling party 15, it determines the optimum routing for the call (step 207). If called party 25 and calling party 15 do not share a local exchange, that is, if local exchange 10 and local exchange 20 are different switching offices, then the TCS 11 of local exchange 10 (shown in FIGURE 1) generates an IAM 75 for transmission to local exchange 20 (step 208).

IAM 75 contains the DASC and UC information received from calling party 15 in step 204. The IAM 75 may be directly transmitted to local exchange 20 or, if necessary, relayed through intermediate exchanges. Alternative sequences for transmitting the distinctive alert information are possible, and contemplated to be within the scope of the present invention (but are not shown). For example, the distinctive alert information could be sent in a separate message once the connection to local exchange 20 is established, or local exchange 20 could at that time query for any distinctive alert information. It may be desirable to have local exchange 20 send such a query in the event that no such information is received, in case the codes were in fact entered by the calling party 15 but somehow dropped during call setup.

When local exchange 20 receives IAM 75 containing a DASC (step 209), it determines which line will carry the call to the called-party subscriber 25 identifie in IAM 75 (step 210), and logic device 40 (shown in FIGURE 1) extracts the UC from the IAM 75 (step 211). Local exchange 20 then determines whether the called-party 25 is off-hook, that is, if line 101 is"busy"or already in use. (step 212). If not, then logic device 40 uses the extracted UC information to determine the corresponding distinctive alert pattern (step 213). Logic device 40 then causes ring generator 35 (shown in FIGURE 1) to send a signal over line 101 to the ringer 26 (also shown in

FIGURE 1) of called party 25 (step 214), as hereintofore described. If local exchange 20 receives a response from called party 25 (step 215), then the calling circuit is completed (step 216). If after a predetermined period no response has been received, then the circuit is released (step 217).

If, on the other hand, local exchange 20 determines in step 212 that line 101 is busy, it further determines whether called party 25 subscribes to call-waiting service (step 218). If not, local exchange 20 releases the circuit (step 217). If called party 25 does have call-waiting service, then local exchange 20 generates a standard call- waiting signal for transmission to called party 25 (step not shown in FIGURE 2).

In a particularly preferred embodiment, if line 101 is busy and call-waiting service is available (steps 212 & 218), then, logic device 40 uses the UC extracted from IAM 75 and determines the corresponding distinctive call-waiting signal (step 219). The distinctive call-waiting signal is then sent to called party 25 (step 220). As with the distinctive alerting, if local exchange 20 receives a response from called party 25 (step 221), then the calling circuit is completed (step 216). If after a predetermined period no response has been received, then the circuit is released (step 217).

If local exchange 10 and local exchange 20 are actually the same switching office, that is, at step 207 it is determined that called party 25 and calling party 15 share a local exchange, then the call can simply be set up as hereintofore described, beginning with step 212.

While the embodiment described above shows the applicability of the present invention in a Public Switched Telephone Network (PSTN), it is equally applicable and useful in Public Land Mobile Network (PLMN), or to calls from a PSTN to a PLMN through an appropriate network gateway, or vice versa. As with calls made within a single network, or between like networks, the called party is alerted by a standard alert signal unless a distinctive alert service code has been received.

Although in the disclosed embodiments each user is alerted through a distinctive ring tone, it will be recognized that the present invention is equally applicable to other types of alerts, such as flashing lights.

In addition, the distinctive alerts referred to herein need not be directly associated with separate individuals. A subscriber could, for example, provide family

members with one distinctive alert service code and business associates with another.

Or a calling party could use one of several available UCs to signal the urgency placed on the particular call.

It is also noted that the order and sequence of many of the steps can be varied without substantially affecting the performance or result of the claimed method. It is also not considered substantially essential that the distinctive alert information transmitted from one exchange to another be identical to that initially received from the calling party, nor is it essential that each different user code result in a completely unique alert pattern. A subscriber may well elect to have, either temporarily or permanently, multiple user codes that produce the same distinctive alert, including some that result in a standard alert pattern.

Although an embodiment of the method and apparats of the present invention has been illustrated in the accompanying drawings and described in the foregoing detailed description, it will be understood that the invention is not limited to the embodiment disclosed, but is capable of numerus rearrangements, modifications and substitutions without departing from the spirit of the invention as set forth and defined by the following claims.