Browse Prior Art Database

Daisy Chained Analog Video

IP.com Disclosure Number: IPCOM000013440D
Original Publication Date: 2000-Dec-01
Included in the Prior Art Database: 2003-Jun-18
Document File: 6 page(s) / 233K

Publishing Venue

IBM

Abstract

The mechanism being disclosed is a daisy chained analog video solution that addresses the key requirements that yield a high quality video "front of screen". One that has a video output with crisp colors and fonts, with proper luminance contrast, as well as proper full scale luminance, while keeping the cost of implementation to a minimum.

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Daisy Chained Analog Video

The mechanism being disclosed is a daisy chained analog video solution that addresses the key requirements that yield a high quality video "front of screen". One that has a video output with crisp colors and fonts, with proper luminance contrast, as well as proper full scale luminance, while keeping the cost of implementation to a minimum.

   Presently, when there are several computer systems installed in a rack, the connections to the KVM (Keyboard, Video display, Mouse) console devices is usually performed by means of a KVM switch/multiplexer such as available commercially with brand names such as Apex*, Cybex* and others. This requires a cabling approach that is expensive, bulky, and cumbersome. This is due to the fact that fairly long cables must connect each system's KVM connectors to the appropriate port connectors in the switch / multiplexer, three device connector pairs resulting in a total of six connectors for each "system to KVM switch" connection This is further complicated when the quantity of systems to be multiplexed is greater than the number of ports supported by a single switch / multiplexer usually four or eight). In such a case, the KVM switch must be connected in a tier / cascade scheme thereby requiring even larger amounts of cabling. See Figure 1.

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An alternate solution consists of connecting the systems to the KVM devices in a daisy chain fashion starting with a cable from the "OUT" connector of a system to the KVM devices, its "IN" connector is connected to the "OUT" connector of the system downstream in the daisy chain, and so on, until the last system in the chain which does not have any system connected to its "IN" connector. This would replace the bulky, cumbersome and lengthy cabling and the switch/multiplexers (and the need for supplying power for them) with chaining cables. See Figure 2.

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However, even though the chaining scheme greatly simplifies the cabling, it introduces some challenges. Any imperfection and/or error introduced by each system/cable stage, or link, in the chain gets compounded with each stage that is added. Imperfections such as those caused by layout, propagation delay differences in the signals, differences in signal attenuation, etc., are compounded by the number of systems and the interconnecting cables. The chaining implementation must provide a multiplexing scheme that results in a video output of good quality with crisp colors and fonts, with proper luminance contrast, as well as proper full scale luminance while keeping the cost of implementation to a minimum. The mechanism described forthwith addresses these requirements, in fact, resulting in an output of higher quality than the traditional approach of using a KVM switch.

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In order to provide crisp colors and the required crisp fonts, with proper lu...