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luckylerado:
X-10 is a relay system with control mostly by PLC at about 125 kHz (PLC here means Power Line Carrier). The switching device is either an electro-mechanical relay, or a solid-state relay (likely a Triac), and in some units also a dimmer.
iwire:
Neither do I call an ordinary wall switch a relay. I was simply pointing that one might extend the definition of a relay to a wall switch, but I would not do that.
For a general definition of relay the following is useful:
http://www.thefreedictionary.com/relay
If one does not use switches in some logical network to directly control the lights, then relays of some sort will be required.
PLC as used in the TED power monitoring system has a great many problems.
Filtering can reduce the problem, but that eliminates broadcast capability. TED interferes with itself, with X-10 and others, and X-10 and others interfere with TED.
A number of statements by TED people are wrong relative to their PLC system.
They use exactly 125 kHz, not something nearby as they describe. This I have determined by both measurement and analysis of their circuit.
They don't just transmit data during or near line voltage zero crossings.
The 1000 system transmits a continuous signal for a packet duration of about 0.1 second or about 6 full 60 Hz cycles. The baud rate is 1200 and there is way too much data to transfer in short segments around 60 Hz zero crossings, and provide new data every 1 second.
The 5000 system has a packet duration of about 0.2 seconds.
In the 1000 system a new packet is sent every 1 second. A maximum of 4 MTUs are allowed. If these were synchronized, then 40% of the available time would be used.
They are not synchronized and therefore interfere with each other at times. The different MTUs float around in time, intereferring at times, and not at other times.
There is no 1 second data available from the 5000 system even though TED implies there is. Data in the 5000 is available in packets that are spaced at about 2 seconds sometimes and at other times with a greater spacing up to around 5 seconds.
I agree that low cost is probably a goal. But it is not low cost if it is not reliable.
GoldDigger:
I have defined PLC in the present context just above.
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