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INCOMING-CALL CALL BACK SERVICE FOR A HANDSET ENGAGED IN CONVERSATION IN A CT2 TWO WAY SYSTEM

IP.com Disclosure Number: IPCOM000007471D
Original Publication Date: 1995-Jul-01
Included in the Prior Art Database: 2002-Mar-29
Document File: 4 page(s) / 160K

Publishing Venue

Motorola

Related People

Ng See Woon: AUTHOR

Abstract

BACKGROUND OF THE CT2 TWO WAY CALLING SYSTEM Figure 1 shows the System Architecture of the CT2 Two Way Calling System. For a CT2 handset to receive incoming call in a call zone, the handset needs to inform the system of its location, either automatically or by manual means; and this is effected in a Registration Call from the TBS to the VLR. The information of the TBS to which the handset is registered is maintained in a database in the VLR. These information together with that ofthe VLR is then presented to the Home Location Register (HLR).

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MOlVROLA Technical Developments

INCOMING-CALL CALL BACK SERVICE FOR A HANDSET ENGAGED IN CONVERSATION IN A CT2 TWO WAY SYSTEM

by Ng See Woon

DESCRIPTION

BACKGROUND OF THE CT2 TWO WAY CALLING SYSTEM

  Figure 1 shows the System Architecture of the CT2 Two Way Calling System. For a CT2 handset to receive incoming call in a call zone, the handset needs to inform the system of its location, either automatically or by manual means; and this is effected in a Registration Call from the TBS to the VLR. The information of the TBS to which the handset is registered is maintained in a database in the VLR. These information together with that ofthe VLR is then presented to the Home Location Register (HLR).

  When there is an incoming call to the handset (with the pre allocated directory number by the PSTN), the SSP serving the caller recognizing this special number will trigger an enquiry call to the HLR for a routing number to redirect the call to the TBS to which the handset is registered to. Notice that this routing number returned is different from that of the handset directory number. The routing number is in fact the directory number of the BRI connected to the TBS. When the call is finally routed through, the appropriate handset is polled and caused to ring.

  During the incoming call for a handset, the PID of the handset is checked against a list of handsets which are currently engaged with the Base Station. If the destination PID is found in the list, the call- ing number of the calling party and the called PID are stored in a CALL-BACK table.

  When any handset hangs up, its PID is com- pared against those in the CALL-BACK table. If the PID matches any in the table, the Base Station automatically dial its corresponding number. Now if the called party responds by sending an ALERT sig- nal, the Base Station will begin to poll the handset and transmits the called number to the handset at the same time. When either party picks up the call, they will hear the ringing tone until the other party connects. At that point, conversation between the two can proceed.

  If the called party is busy, a retry is made some predetermined time later. Prior to the attempt to reach the calling number, a two fold check is made to see that the handset is free to accept a call. First, the PID is checked to ensure that it is not engaged on another link with the Base Station, then, silent polling (no ringing) of the handset is done to deter- mine if it is still within range of the Base Station. Only when both these conditions are met will the Base Station automatically try to reach the earlier calling number, and count the attempt.

  A maxim...