How IR Repeater Systems Work
An IR repeater system takes Infrared (IR) light coming from your remote controller and converts it to an electrical signal that can be easily distributed over electrical wiring to one or more IR remote controllable components. How this can help improve your system and allow you more flexibility in multi-room applications is something we'll attempt to answer and explain.
IR Repeater System Components
What are the usual components of an IR Repeater System and what do they do?
The Target, often called an "IR receiver", receives the modulated IR light waves transmitted from your remote controller and converts them to electrical signals for distribution or extension.
The Connection Circuit or "Connection Block"
The way in which the receiver(s), emitter(s) and power supply are interconnected. This can all be wired together with or without any kind of terminal strip or manufactured connection block, or with such products. Using a connection block results in a system that is easier to expand and reconfigure.
The Emitter sometimes called an "IR bug", "IR blaster", or "IR flood" is the device that converts the electrical signal back from the distributed electrical signal to a modulated Infrared band light signal which is then retransmitted by light waves to the IR controlled device, such as a DVD player, Receiver or Display. IR Bugs are attached on the receiving device directly over the devices IR receiver port. IR Floods are high output emitters placed in front of several devices to emit signals to all of the devices from one emitter device.
The System and Potential Problems
Basically the whole system should be "transparent" to the remote control and remote controlled devices. The conversion to electrical signals, distribution and conversion back to IR light should have no detrimental effects on the light signals, or at least have a negligible effect on the functionality. Seems like it should be pretty simple to do, right? Well, in fact, there's a bit more to it than that. The devil is in the details, as usual for all this fun AV stuff.
Problem #1: Power
All this stuff needs power to work, and this causes limitations in the number of targets and emitters you can use with a given rated power supply. Target power outputs and emitter power requirements vary as well. Cable lengths and gauges can also be a factor, the longer the wire and higher the gauge the more likely that it could cause enough power loss to have an effect on the system.
Problem #2: Light Bends
Pesky light waves stubbornly refuse to turn corners, lose their strength with distance, bounce all over the place causing interference patterns and are also emitted by room lighting, the sun and of course your display which "rather annoyingly" (ha ha) puts out lots of light itself. Unfortunately all these light sources tend to put out light at frequencies in the infrared band in addition to the light waves you can see. Putting an IR receiver right next to your lovely Flat Panel display subjects the infrared light coming in to the various frequencies of light going out, causing interference. The sensor itself generally accepts a wide frequency range and needs to be properly filtered to remove non infrared band signals. The closer the receiver can restrict the incoming light to just the frequencies put out by the remote control the purer the signal will be, and the more reliable the whole system will be.
Problem #3: Duplicate IR Codes
IR code conflict is a bear. If a manufacturer of a device inadvertently uses an IR code that is used by another manufacturer then you get two devices responding in their own unique ways to a signal meant for only one device. By its nature, an IR distribution system sends all of the signals to all of the devices. So, if two devices use the same code for a function, both devices will receive that code and will perform the function. This type of thing is mainly caused by manufacturers who are not privy to the codes of the other manufacturers. In addition, different manufacturers of remote controls use different protocols and different carrier frequencies to transmit these different infrared signals. As usual, the manufacturers love NOT getting together and creating standards. Unfortunately for us users, this sometimes makes using their products less of an easy and happy experience.
Problem #4: Hypersensitive Equipment
Emitters can over-power the equipments IR sensor. Low power emitters and adjustable output emitters are available for equipment that is overloaded by standard or high power emitters. This is especially true for cable and satellite TV boxes.
Problem #5: Simplifies Distribution, Not Remote Control
The system does not eliminate the requirement for multiple remotes. An easy to use universal remote will provide an easy one touch control for a sequence of operations either by macros or simple commands.
The IR System Components In more detail
IR targetsRemote controls today are mostly "IR" based controllers which use electromagnetic waves in the Infrared band of "Light", which is just below our eye's visible light wavelengths. Infrared light is used in quite a lot of applications. From those "night vision" goggles used by the military (and the freak in Silence of the Lambs) to ultra cool uses in Astronomy and Art history. Well, ok, "ultra cool" to the geek in us.
Tech Note: Some remotes use "RF" frequencies. These are radio frequencies which are below infrared wavelengths in the electromagnetic spectrum.
There are RF to IR remote conversion devices available if you need to convert an RF device to work with your IR remote control repeater system.
The target's goal is to receive the light that an IR remote control puts out and convert it into electrical signals. The electrical signals must be filtered to remove the frequencies not within the frequency range emitted by the controller. If the target does a poor job of filtering, you get a noisy signal. Garbage in, garbage out is very much the case here. This is what makes the targets you use the most crucial part of the system. While you could say that the IR signals sent by the remote are analogous to digital signals, the light waves hitting the target are coming from all over the room and are more similar to analog. The target has the job of filtering out all of the off-band garbage and converting just the IR signal into electrical signals. Poor quality filtering can cause lots of indecipherable messages to be sent. Errors can have strange, unpredictable effects.
The Electrical Distribution System
IR blockOnce converted to electrical signals the job is relatively easy. It is a matter of distributing these signals to all of the component devices; your Receiver, DVD player, Cable TV box, or TV where they will be converted back to infrared light to control the device. For a single room system this is pretty easy. A quality IR Receiver can drive as many as 10 emitters reliably - way more than most people need. If the setup is pretty simple and numbers of receivers and emitters is low enough, then several hundred feet of solid cat5 wire should work fine with quality IR components without causing any additional limitations.
In more complex multi-room setups with long cable runs the limitations of even high quality power supplies comes into play. Amplified Connection blocks are your best bet for these setups. This way the receivers as well as targets will have plenty of power for reliable operation. Using Amplified Connection Blocks is also necessary for large, distributed systems or long extensions. With Amplified connection blocks, the IR signals themselves are amplified, unlike with powered connection blocks where the power is simply used to drive the receivers and emitters.
IR emitterThe Emitter's job is pretty easy, it simply takes the electrical signals it is given and converts the signal into low frequency red (IR) light which is output to the IR sensor on the IR controlled device. IR bugs attach to the device (DVD, receiver, etc) directly over the IR receiver of the particular unit. Low power emitters won't typically overdrive more sensitive components, but if you have trouble, adjustable output emitters allow adjustment to "fine tune" the output to make problematic devices behave.
IR Floods (emitters that are designed to shoot at multiple items) should be placed in a centralized location in front of, and pointed at the desired devices to control. The minimal distance from the emitter to the devices can vary with the flood emitter's dispersion and output capabilities as well as the receiving component's sensitivity. If you have little space between the desired location for a flood emitter and the components to be controlled, using separate IR bugs is the best way to go. There are light "guide" devices like Audioplex's IR Prisms that can possibly improve the performance of IR flood emitters if used right, while blocking out unwanted light from off axis sources.
The Power Supply
The power supply quality and rating is important. The necessary rating depends on the power needed to drive the various components and cable runs. The reliability of the whole system is dependant on the power supply not failing. These systems, by definition, run 24/7 unless they are connected to one of your system's accessory power ports. The amperage required depends on the number of receivers and emitters connected. Receivers usually draw much less power when idle than when active. Having lower power usage specs on devices obviously becomes more critical as you add more and more of them. Long term reliability is obviously also improved with more efficient, lower power drawing devices since the power supply is the most common point of failure.
Closely spaced multi-room systems can often get by with using powered blocks in each room to make sure the receivers and emitters have plenty of power to drive them. Larger scale distribution systems should always use amplified blocks which power the devices locally as well as amplify the IR signals to account for signal degradation over the longer runs of wire.
IR systems in their most robust forms can be quite complex. We are only giving the basics here. They can transmit IR signals from many targets to many components in numerous systems over thousands of feet, they can integrate messaging signals for display on wall plates or other displays, or they can even control lighting, drapes or other devices. In this article we have hopefully answered some of your basic questions about how IR remote repeater systems function and how to go about using them in a simple home theater environment.
Also see are Guide: How to Install an IR (Infrared) Repeater System