Leviton's new DHC receivers with Intellisense; deliver the reliability you depend on in powerline carrier home automation products -- even in applications where electrical "noise" is present on the AC line. And Leviton's Intellisense circuitry assures excellent noise immunity without reducing command signal sensitivity so that top performance of the DHC system is assured.
Leviton's new DHC receivers with Intellisense deliver the most reliable performance of any powerline carrier home automation products available today.
What is AGC?
AGC or Automatic Gain Control is a new enhancement available on certain X10 compatible products. It significantly enhances the ability to detect X10 signals in the presence of noise. Leviton's AGC claims to improve X10 signal reception to the point that signal bridges and noise filters are unlikely to be required in homes under 4000 sq. ft. HomePro AGC is of a different design than the Leviton AGC and may not be as sensitive.
Noise on the line -- a part of every electrical system
Powerline carrier home automation systems are easy to install because the home's existing AC wiring is used to carry command signals. However, in many homes, electrical interference can prevent receiver modules from operating properly. Electronic equipment found in virtually every household generates disruptive noise interference: TV's, VCR's, audio equipment, personal computers and peripherals, fax machines, electronic lighting ballasts and many other electronic devices.
How noise can disrupt powerline carrier systems
Powerline carrier systems transmit and receive command signals at the zero crossing of the AC power curve. That's because electrical noise is at a lower level here than at any other point in the cycle. The zero crossing point is the Signal Window where receiver modules listen for the special coded comman sequence. If the receiver hears a steady stream of signals in every signal window, it interprets this as random noise and does not respond.
Figure 1 shows a typical powerline carrier command signal.
Note that there are "empty" signal windows in the coded sequence.
Figure 2 shows what can happen when there's noise on the powerline
while a command is being transmitted. The noise fills in all the
signal windows, disrupting the coded sequence. As a result, the
receiver cannot hear the common signal and does not respond.
Amplifying the command signal may not solve noise problems
Problems from noise interference are more related to receiver sensitivity than to signal strength. The sensitivity of a receiver determines the minimum amount of signal it can recognize. In order to deliver reliable performance in a variety of applications, powerline carrier receivers must be sensitive to command signals that are lower than 1/10 of a voly (.100 volts). Boosting the command signal does not change a receiver's sensitivity. No matter how powerful the command signal is, the receiver will still be sensitive to noise that's only a fraction of a volt, and noise will still be capable of disrupting the system's operation.
Automatic Gain Control is needed, but not just any kind
Automatic Gain Control (AGC) is a special circuit that adjusts receiver sensitivity to help eliminate noise interference. While Automatic Gain Control can be very effective in reducing noise problems, some types of AGC cirtuis yield mixed results when it comes to overall system performance. Up until now, only a "non-gated" type of AGC was available in powerline carrier receivers. Non-gated AGC circuitry is not symchronized with the sugnal window. Instead, non-gated AGC desensitizes a receiver to high noise levels that occur throughout the entire AC cycle. Powerline carrier receivers are only affected by noise within the signal window, which is the lowest level of noise in the entire AC cycle.
Therefore, non-gated AGC desensitizes the receiver to accommodate high noise levels that do not even affect receiver performance. That means the non-gated type of AGC currently available can desensitize the receiver from noise to such a degree that it also desensitizes it to command signals. There are installations where non-gated AGC circuitry can create as many problems as noise does.
A New Built-In Feature Provides Outstanding System Reliability
Leviton's DHC receivers feature Intellisense, the right type of Automatic Gain Control
Leviton DHC receivers use Intellisense, a special gated type of AGC, to help eliminate hoise problems. The Intellisense gated AGC ciruit is ideal for powerline carrier systems because it only operates during the signal window when receivers listen for command signals. Noise levels in the signal window are never as high as they are during other portions of the AC power curve. Therefore, Leviton's Intellisense gated AGC will desensitize a receiver to noise signals with only a minimal reduction in command signal sensitivity. The result: Problems from noise interference are dramatically reduced without affecting overall system performance.
Leviton's new Intellisense is built into DHC wall-mounted switch and receptacle receiver modules. These modules are installed exactly the same way as they were before, and there's no change in their popular Decora styling, either.
NEW! DHC Dimmer Switch Modules with Intellisense plus enhanced performance features
Leviton DHC Dimmer Switch Modules not only feature Intellisense for outstanding performance and reliability; they also provide new performance features for added comfort and convenience.