Telephonic communications – Supervisory or control line signaling – Using line or loop condition detection
Reexamination Certificate
1999-11-01
2004-04-20
Barnie, Rexford (Department: 2643)
Telephonic communications
Supervisory or control line signaling
Using line or loop condition detection
C379S412000, C379S399010, C379S413000
Reexamination Certificate
active
06724889
ABSTRACT:
BACKGROUND OF THE INVENTION
1. The Field of the Invention
The present invention relates to the field of communication networks and systems. Particularly, this invention relates to interfacing with telecommunication networks requiring a specific interface characteristic for compatible interaction with the network. More specifically, the invention relates to maintaining the interface characteristics and requirements for the dissipation of line side power by a telecommunications terminal interface device, where the line side power is used to provide operational power to line status indicators.
2. Prior State of the Art
Modern data transmission devices such as computers are increasingly used in applications that require exchange of data over a communication network. Some of the more popular communication networks used to propagate data are the well established telephone networks. Such networks were originally designed to accommodate, and therefore propagate, the transmission of voice conversations which include very specific bands of frequencies. Individual countries have implemented unique power and frequency standards relating to their particular implementation of telephone networks.
While the inter-operation specifications differ for national telephone networks, they each require the modulation of computer data in order to comply with the individual specific bandwidth requirements. To facilitate the modulation and the complementary demodulation processes, devices known as modems (MOdulate/DEModulate) have become ubiquitous. In order to compatibly inter-operate with the telephone network, a modem must perform certain “telephone handset” functions to appear to the telephone network as though it were a legacy telephone handset-compatible device.
Since legacy telephone handsets typically employed electronic circuitry requiring higher power levels, the legacy telephone networks continue to require modem communication devices interfacing therewith, such as modems, to appear to the telephone network as though it were a legacy handset by adhering to specific or specified power ranges which include drawing from the telephone network a specific voltage range as well as a specified range of current from the telephone network.
An example of a legacy telephone handset function is when the modem is “off-hook.” Off-hook functionality requires the modem to signal the telephone network that information is either going to be sent by the modem to the telephone network or that the modem is ready to receive information from the telephone network. Telephone network specifications typically require that the modem or other terminal device signal an off-hook condition by drawing or sinking a specified amount of current from the telephone network. Traditionally, such drawn current was utilized by a telephone to “power” the telephone during use.
Often existing communication networks are commonly used by modem networks, for example the POTS or other internationally similar networks are used to expand connectivity to the network. A POTS network provides an archaic interface that requires a specific amount of off-hook current to be drawn. The typical domestic line side current available is generally in the range of 10 mA to 40 mA, with the preferred range being around 15 mA. Some international telecommunication standards require that a modem's hold circuit must be able to sink around 120 mA of line current.
In a modem application, where a digital device such as a computer requires appreciable power, the current drawn by the modem is a fraction of the power used by overall digital device. As such, attempts to use the line side power provided by the off-hook condition are typically unnecessary and therefore wasted as the modem functionality derived power either from an external independent power supply or by sharing the power supply of the computer or host device. Furthermore, there is considerable fluctuation of the available line side power, making it difficult to regulate the use of line side power with the delicate modem circuitry.
Another problem facing designers of telecommunication interface devices are the variety of telecommunication specifications propagating worldwide. Those familiar with global telecommunications standards appreciate that various countries have implemented individual and oft times incompatible telephone network standards thereby precluding handsets from inter-operating in various national inter-networks. In the present global climate various countries have settled upon common standards for enabling compatibility between national telephone networks. Once such standard that has been adopted in the majority of European community countries is the TBR21 standard which propagates a specification of standards to which inter-operating terminal equipment, such as telephone handsets and modems, must comply in order to compatibly inter-operate on the European community telephone network.
One such requirement propagated in the specification is a power curve specifying a voltage and current range within which the terminal equipment must inter-operate. Those familiar with the electronic arts appreciate that the voltage and current requirements as propagated in the TBR21 specification are substantial in view of modern, low power electronic circuitry. While electronic devices and circuitry can be implemented in accordance with the higher power specifications of the modem standard, electronic components subjected to higher power levels exhibit earlier power failures and therefore decreased reliability due to the enhanced power. It should be pointed out that while electronic components capable of absorbing higher power levels while maintaining high reliability are available, in mass manufacturing global environments, such high reliability, high power components tend to be impractical due to their high cost and larger physical dimensions, especially in view of an ever increasing miniaturization of electronics.
In the advent of miniaturization, computers have become increasingly more integrated and as such have become more mobile and portable. One overriding design concern with portable computers is power management. In a portable environment, all of the operating power for the computer and any peripheral devices, such as modems, must be resident within the computer. Hence, portable computer batteries are heavily taxed by all of the attached peripheral devices. Therefore, the inefficient use of available line side power affects the overall performance of the digital system by increasing the overall power usage and decreasing the battery life, resulting in a overall higher power dissipation in the hold circuit. Specifically, power is used from the computer battery to indicate the line status of the modem and power is dissipated to comply with the specifications of the telecommunication network.
As previously mentioned, the power drawn had heretofore been unusable by terminal interface devices, such as modems, since older terminal interface devices required an amount of power for operation beyond what was available. With miniaturization and development of lower power designs, the available power from, for example, the POTS is sufficient to be employed for useful power to electronic components on a network interface device. However, the fluctuation of available line side power is still problematic. The network interface device cannot depend on a variable power source, furthermore, the modem may not introduce noise onto the line side of the communication network which prevents attempts to regulate line side power.
Yet another problem in the realm of data transmission devices is the varying telecommunication interface specifications. The similarity of the network jacks or interface devices connecting the computer to the communication network is the source of considerable confusion. Attempts to connect an analog modem to the phone jack of a digital system result in excessive line current that can fuse the low power circuitry of the modem. To prevent this type of hardware meltdown, some communication
Giles Rick D.
Price Tim Urry
3Com Corporation
Barnie Rexford
LandOfFree
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