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| EMagazine Volume 4 Issue 6 December 1999 |
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Toys Article - December 99 - [HTI Home Page] |
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The 3445 connects to four tiny infrared (IR) sensors. Each of these is designed to be pasted on to the built-in infrared sensor on devices such as VCRs or satellite receivers. The 3445 then receives a signal from a small IR target that sits on one or more of the TVs that are driven by the distribution system. |
This article is being reprinted courtesy of Triple D Publishing. Dr. Frank Baylin, president of Baylin Publications, has worked as a consultant in the satellite industry since the early 1980s. He has also written over 15 books, produced videos and authored software during this period. A catalog of Baylin Publidcation's best-selling products can be requested at (800) 483-2423 or via the Internet at www.baylin.com |
In a previous article (OnSat Magazine Issue #41, Oct. 12-18, 1998), we discussed one method of distributing satellite television programming to two or more rooms in your home. When the objective was to have completely independent selection of any channel on any particular satellite, I explained how a separate receiver in each room could be hooked into what is known as an IF distribution system. There are, however, other alternatives.
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THE BASICS
How does a cable system deliver a mix of channels to a large number of subscribers? At the cable TV headend, television signals are received from a variety of sources including satellite, VCRs, DVDs, off-air broadcasts and fiber optic links. These are first demodulated, or stripped down, to the raw signal. This is accomplished by devices such as satellite receivers. In fact, there may be banks of as many as 200 satellite receivers with each tuned to a different channel at some cable TV headends. The resulting raw or "baseband" signal can be interpreted by a television monitor. However, a standard TV set requires an amplitude modulated (AM) signal and could not decipher the baseband signal. (You can get a higher quality picture from the baseband output rather than the modulator output of your VCR when feeding a TV monitor because it does not have to pass through one more processing--modulation--step.)
After the baseband signals from the various sources are cleaned up and filtered to remove unwanted components, they are then remodulated to become AM signals. Each of these AM television signals is assigned a different channel number. For example, Discovery Channel may be found on cable channel 43 and Disney on cable channel 47. It is totally arbitrary. This assignment is at the discretion of the cable TV operator. There is one AM modulator for each channel in use. Finally, all the channels, each occupying its own frequency band, are combined on one cable and routed to subscribers on the cable network via amplifiers and other components.
MAKE IT WORK FOR YOU
How does all this technical information apply to installing a distribution system in your home? The company that I had mentioned earlier, Multiplex Technology, (800) 999-5225 has developed a relatively inexpensive line of home components that function like cable TV headends. Their modulators accept two, three or four source inputs and distribute the AM television signals to up to eight different TV sets. Unlike the more complex setup at a cable headend, these "Channel Plus" modulators are all contained in one small (1.5 x 7.9 x 5.5 inches) box (see Figures 1 and 2 below). (Other configurations are also available.)
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Figure 1. Channel Plus 3445 Modulator. This illustrates the 3445 modulator with its 4 video/audio source inputs, four IR remote inputs, its coax output as well as the front panel controls. |
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Figure 2. Channel Plus 3445 Distribution Panel. The 3445 modulator feeds a coaxial output into this panel. This device also accepts an input from either an off-air antenna or a cable TV hookup. Either one (4 program sources) or two modulators (8 program sources) are accepted. |
I installed the Channel Plus 3445 system in our home a few months ago. This modulator easily fit into our entertainment center cabinet. It has four built-in modulators, each of which can be set to any VHF or UHF channel. It also comes with a small distribution amplifier/panel that has outputs to drive up to eight TV sets.
Installation was surprisingly simple. I chose UHF channels 15, 25, 35 and 45 as outputs from the 3445 so the signals would not interfere with local Denver VHF channels 2, 4, 6, 9 and 12 or UHF channels. Channel assignments can be easily entered from buttons on the front panel of the 3445. The four inputs to the 3445 are from our satellite receiver, VCR, DVD and a video camera in the baby's room. One coaxial cable then connects the output of the 3445 to the distribution panel, which I installed in a wall behind the entertainment center. This box accepts an input from my off-air antenna and from one or two 3445 modulators. You would use two modulators if you wanted to modulate and distribute eight channels. Its eight outputs were routed via eight coaxial cables to eight rooms in our home. The built-in amplifier in the distribution panel compensates for signal losses that occur in the coax run to the remote TVs.
But this is only half the picture! The 3445 connects to four tiny infrared (IR) sensors. Each of these is designed to be pasted on to the built-in infrared sensor on devices such as VCRs or satellite receivers. The 3445 then receives a signal from a small IR target that sits on one or more of the TVs that are driven by the distribution system. As shown in Figure 3, this device accepts the coax from the distribution panel and outputs a short run of coax to the TV set. The end result is that you can use the remote from your VCR, DVD, etc. to control all functions such as volume, rewind, channel selection, etc. from any of the TVs equipped with the IR target. Now, for example, if we want to watch satellite TV in any room, we simply tune the TV set in that room to UHF channel 25 and select channels with the remote. It's that easy.
Figure 3. Distribution System.
Here the 3445 modulator is fed by a VCR, satellite receiver, DVD player and a
video camera. The hookup of the IR target is also illustrated.
All in all, this is quite a well- designed and powerful, yet simple, system. The end result is that you can control a VCR, DVD or satellite receiver and view these and, if you wish, the picture from a remote TV camera from any TV on the system.
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