Appliance Control: Making Things Do Stuff - Smart Home Automation with Linux and Raspberry Pi - page 46

All-in-One Remotes
There are so many combined all-in-one remotes that it's difficult to know which to get without trying them.
Unfortunately, that is what you must generally do, because each one has some quirk or another that makes it
unsuitable for your particular set of devices.
Although several varieties of “all-in-one” remotes exist, they are not created equally. You need to consider the
specifics of each device you want to control because in the United Kingdom and Ireland, Sky Plus, for example, uses
a slightly different IR protocol than normal, so unless your remote is specifically designed to handle it, you device will
appear mute.
A number of learning remotes are available now, and these can prove a good investment. Another useful feature
is a macro , which will store a number of commands in sequence. For example, a movie mode macro could switch the
TV to DVD input, switch on and eject the DVD tray, and set the HiFi to accept a DVD input.

IR Relays
These devices overcome the line-of-sight problem by retransmitting IR signals from one place to another. They
consist of both a transmitter (which watches for IR signals and relays them over the air) and a matched receiver
(which replays the same IR message to the device). With a suitable transmission range, you can remotely control the
downstairs TV from upstairs.
Sometimes it's possible to have multiple transmitters, one in the kitchen and one in the bedroom, say, that both
send the signals to one place, allowing you to remotely control the TV from anywhere.
By the same token, it is sometimes possible to have multiple receivers, enabling an all-in-one remote to send
commands from the bedroom to both the TV downstairs and the HiFi in the next room. However, this configuration
is less common because, if you've installed an IR relay, the location of the equipment doesn't matter, so it is usually
in the same physical location; therefore, you only need to mount one IR receiver, which sends the relayed signal to all
devices at once. If the devices are fairly close to one another but the receiver can't see both devices, then it is usual to
use a Y-splitter and two IR LEDs rather than buying another receiver unit.
Communication between the two transmitter and receiver is done through one of the ways outlined next.

Over the Aerial Cable
If your primary purpose is to relay IR controls for a TV, then you can get devices that embed the IR data onto the
existing coaxial aerial cable, hiding it with similar results to X10. The Labgear MRX120 HandyLink, for example,
provides such a solution. Naturally, this approach requires an aerial cable in each room, which there will be if your
focus is TV control. If the aerial cables already exist, then scaling up is easy, because adding extra amplifiers is fairly
cheap and is a simple plug-and-play affair. Without existing cables, however, this can be more trouble than it's worth,
given the IR-RF-IR possibilities, but it can provide a solution where RF reception is especially poor.
In both cases, it is impossible to watch different channels in each room, even with Sky, because it's distributing a
single signal from the tuner.

N You may need an IR bypass kit when passing IR signals over coax cables because the messages get muddled
when passing through distribution amplifiers.

Note