1. Field of the Invention
This invention relates generally to telecommunications, and, more particularly, to performing off-hook detection and control of power-mode.
2. Description of the Related Art
In communications systems, particularly telephony such as a Plain Old Telephone System (POTS), it is common practice to transmit signals between a subscriber station and a central switching office via a two-wire, bi-directional communication channel. A line card generally connects the subscriber station to the central switching office. The functions of the line card include supplying talk battery, performing wake-up sequences of circuits to allow communications to take place, and the like. Voltage signals are processed and conditioned when being driven onto telecommunication lines.
POTS was designed primarily for voice communication, and thus provides an inadequate data transmission rate for many modern applications. To meet the demand for high-speed communication, designers have sought innovative and cost-effective solutions that would take advantage of the existing network infrastructure. Several technological solutions proposed in the telecommunications industry use the existing network of telephone wires. A promising one of these technologies is the Digital Subscriber Line (xDSL or DSL) technology.
xDSL is making the existing network of telephone lines more robust and versatile. Once considered virtually unusable for broadband communications, an ordinary twisted pair equipped with DSL interfaces can transmit video, television, and very high-speed data. The fact that more than six hundred million telephone lines exist around the world is a compelling reason for these lines to be used as the primary transmission conduits for at least several more decades. Because DSL utilizes telephone wiring already installed in virtually every home and business in the world, it has been embraced by many as one of the more promising and viable options.
There are now at least three popular versions of DSL technology, namely Asymmetrical Digital Subscriber Line (ADSL), Very High-Speed Digital Subscriber Line (VDSL), and Symmetric Digital Subscriber Line (SDSL). Although each technology is generally directed at different types of users, they all share certain characteristics. For example, all four DSL systems utilize the existing, ubiquitous telephone wiring infrastructure, deliver greater bandwidth, and operate by employing special digital signal processing. Because the aforementioned technologies are well known in the art, they will not be described in detail herein.
DSL and POTS technologies can co-exist in one line (e.g., also referred to as a “subscriber line”). Traditional analog voice band interfaces use the same frequency band, 0-4 Kilohertz (KHz), as telephone service, thereby preventing concurrent voice and data use. A DSL interface, on the other hand, operates at frequencies above the voice channels, from 25 KHz to 1.1 Megahertz (MHz). Thus, a single DSL line is capable of offering simultaneous channels for voice and data. It should be noted that the standards for certain derivatives of ADSL are still in definition as of this writing, and therefore are subject to change.
DSL systems use digital signal processing (DSP) to increase throughput and signal quality through common copper telephone wire. It provides a downstream data transfer rate from the DSL Point-of-Presence (POP) to the subscriber location at speeds of up to 1.5 megabits per second (MBPS). The transfer rate of 1.5 MBPS, for instance, is fifty times faster than a conventional 28.8 kilobits per second (KBPS) transfer rate typically found in conventional POTS systems.
Telephonic communication devices may be integrated into various electronic devices, such as computers, for example. Digital communications via data network lines may be made possible by these telephonic communication devices. Some of these devices may be remote devices where power consumption is of concern. When a telephonic communications device is integrated with these electronic devices, power consumption may become problematic. In order to monitor for communication signals, a minimum amount of power is required. Generally, the telephonic communication devices may be able to detect a communications state, such as an off hook state to determine whether full communication operation should to be implemented. However, one of the problems associated with the prior art is that the output detection is a high power operation and consumes an undesirable amount of power.
Designers have attempted to alleviate some of these problems by providing for a voltage change when a communication event, such as the reception of a ringing signal, occurs. However, the switches utilized in the state of the art devices to perform this function are generally only capable of changing the output voltage to accommodate for different communication events. This causes an enormous amount of power consumption to occur during the detection and operation of the telephonic communication devices. A simple voltage change does not alleviate all of the power consumption concerns. Efficiency in switching between power modes is generally less than desirable when simply performing a voltage change or switch.
The present invention is directed to overcoming, or at least reducing the effects of, one or more of the problems set forth above.