Pulse or digital communications – Transceivers – Modems
Reexamination Certificate
1998-02-04
2001-09-04
Vo, Don N. (Department: 2631)
Pulse or digital communications
Transceivers
Modems
Reexamination Certificate
active
06285706
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to modems used in digital communications and more particularly to the arrangement of components forming the modem.
2. Description of the Related Art
As the computer market becomes more global, a manufacturer obviously wishes to be in as many countries as possible to increase its market share and revenues. However, this internationalization has created a number of problems in many areas. Everyone is familiar with the problems of the different languages and there are various solutions to this set of problems. Another common problem is voltage differences for the AC lines, but this is also a well known problem and can be readily handled by uainf different power supplies or ones that can handle multiple input voltages.
A lesser known area of international concern is in the modem area. Each country has different telephone connections and different electrical standards for the telephone interface. In the past, this has always required certifying the entire modem for each country in which it is to be sold. This has resulted in a tremendous logistical problem, and therefore, lesser distribution of many modem products. It was not worth the time and effort to qualify a modem in many different countries each time there was a change to the modem design, as the entire qualification process had to be repeated. This qualification problem either increased the cost of modems or limited the technology available. Therefore, there is a need for a modem which can be easily upgraded without requiring recertification with each upgrade.
SUMMARY OF THE INVENTION
A modem according to the present invention separates the modem into two portions, a modem engine portion and a data access arrangement (DAA) portion. Only the DAA portion needs to be certified; the modem engine portion does not require certification. This allows the performance and capabilities of the modem engine to be upgraded as desired. The upgraded modem engine is then connected to the previously certified DAA portion. Thus, upgrades to the modem can be easily performed and recertification is not required.
A modem according to the preferred embodiment places the host computer interface, the modem microcontroller and the digital signal processing (DSP) components on the modem engine board. The DAA board includes the codec and the remaining standard DAA components, such as ring detection and hybrid circuitry. All interfaces between the DAA board and the basic modem engine board are done using digital signals. No analog signals whatsoever are transmitted and all digital signals either drive relays or are provided as outputs of optoisolated components, except for those digital signals provided to and from the codec. Therefore, no analog signals are transmitted from the board, only digital signals. The certification bodies do not have concerns with the transmission of the digital signals, only with analog signals which are not properly isolated. Therefore, with a modem designed according to the present invention, the certification bodies require qualifying only the DAA board containing the DAA components and the codec and do not require recertifying the modem engine board with each change to the components on the modem engine board.
Further, the DAA board is contained and fully encapsulated in a housing, preferably a plastic housing, so that all of the high voltage circuits are not accessible to the user without destruction of the housing. Therefore, the various safety bodies also are satisfied with the design.
Therefore, by the use of a modem with the components arranged in separate circuit boards as indicated according to the present invention, international certification is required of only a limited component set, with changes to the remaining components being made freely and not requiring certification.
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Modem: Anpassung auf französisch (1989).
Nagel Paul E.
Skinker Benjamin H.
Watts Robert F.
Compaq Computer Corporation
Sharp Comfort & Merrett P.C.
Vo Don N.
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