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A Summing Circuit Bus for Attaching Audio Devices to Personal Computers

IP.com Disclosure Number: IPCOM000041210D
Original Publication Date: 1987-Dec-01
Included in the Prior Art Database: 2005-Feb-02
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Heath, CA: AUTHOR [+3]

Abstract

A technique is described whereby an audio summing circuit bus is incorporated, into personal computer (PC) circuitry, so as to enable multiple audio devices to share a bidirectional bus without overloading output circuitry.

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A Summing Circuit Bus for Attaching Audio Devices to Personal Computers

A technique is described whereby an audio summing circuit bus is incorporated, into personal computer (PC) circuitry, so as to enable multiple audio devices to share a bidirectional bus without overloading output circuitry.

The audio summing circuit provides the means of having good quality speech producing devices coexist with the digital logic circuitry in the PC. It enables multiple audio receivers and drivers to be attached to a common bus and thereby operate in parallel with a digital bus. It provides an inherent self limiting audio level in that the more the devices that are simultaneously driving the bus, the greater the load on the bus.

The bus is a voltage summing bus used to enable any audio device to communicate with any other device in the audio frequency range. It consists of audio signal line 10, as shown in the figure, audio ground line 11 and terminating resistor 12, typically 600 .

Drivers 13, used to drive audio signals to the bus will go through resistor 14, typically 1200 . The ratio of the drive resistor and terminating resistor optimizes the voltage drive requirements of the drive amplifiers and the attenuating effects caused by more than one drive resistor attached to the bus. This attenuating effect is desirable since it prevents the bus from being overdriven as more drivers are added to the bus. Each driver has a built in means of controlling the output level so as to...