Browse Prior Art Database

DTMF/DP Card

IP.com Disclosure Number: IPCOM000042940D
Original Publication Date: 1984-Jun-01
Included in the Prior Art Database: 2005-Feb-04
Document File: 3 page(s) / 54K

Publishing Venue

IBM

Related People

Kimberly, DW: AUTHOR [+4]

Abstract

This integrated circuit card serves as a pooled resource for digit number registration in a computer-controlled telephone call switching system suitable for PABX applications. One or more such cards are integrally attachable to an IBM Series/1 processor, along with switch cards and other cards described in [1,2,3] for modularly constructing a variety of "intelligent" switching systems. Each registration card can receive digit information signals in the form of either discrete (dial) pulses (DP) or DTMF (dual tone multi-frequency) functions associated with audible tones; hence, such cards are termed "DTMF/DP" cards. Referring to Fig.

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DTMF/DP Card

This integrated circuit card serves as a pooled resource for digit number registration in a computer-controlled telephone call switching system suitable for PABX applications. One or more such cards are integrally attachable to an IBM Series/1 processor, along with switch cards and other cards described in [1,2,3] for modularly constructing a variety of "intelligent" switching systems. Each registration card can receive digit information signals in the form of either discrete (dial) pulses (DP) or DTMF (dual tone multi-frequency) functions associated with audible tones; hence, such cards are termed "DTMF/DP" cards. Referring to Fig. 1, a DTMF/DP card contains four separately operable reception circuits 1, four FIFO (first-in, first-out) memory buffers 2 associated with respective circuits 1, a multiplexing circuit 3 for multiplexing contents of the buffers 2, a microprocessor controller 4, two circuits 5 for transmitting dual tone multi-frequency signals and two transmitting circuits 6 for buffering and transmitting dial pulse signals. The inputs to the reception circuits, taken, for instance, from telephone set lines and telephone company trunk lines through line adapter cards and switch cards (not shown), are converted into digital functions representing received digit information. The central (Series/1) processor and microprocessor 4 communicate via bus 7, and when the central processor is ready to process call digits accumulated in a buffer 2, it commands the microprocessor which then controls the multiplexer 3 to retrieve the digits and forward them (to the central processor) via bus 8. Upon receiving the call digits, the central processor determines if a path (line or trunk) is available for completing the call (in or outbound) connection. If the call is outgoing, the switch connection made by the central processor effectively links the output of one of the transmission circuits 5, 6 through a trunk adapter cord to an outbound trunk line (extending a line into the public telephone network). In this case, the central processor transfers call digits to microprocessor 4 (which may be different from those originally dialed or tone keyed by the calling party) along with instructions indicating which circuit 5, 6 has been selected. The microprocessor passes these digits to the selected circuit (reforming them to the required two-out-of-eight code format if one of the tone transmitters 5 has been selected), and that circuit transmits corresponding analog signals of appropriate form and power level (pulses if a circuit 6 was selected, tones if a circuit 5 was selected) through the connected switch card connection and trunk adapter card to the selected trunk line (the switch card connection circuits are structured to sustain transfers of either analog or baseband digital signals, and can thereby handle such dial number signals as well as analog voice or digital data). For incoming or locally directed calls, the central p...