Which One Should I Use, Part V (Preamble)

Well, hello again, you gluttons for punishment. Don’t you have anything better to do? (I wonder just how many of you are reading this at work, hoping that your boss doesn’t catch you.) To all of you who emailed me to cast your vote, I thank you. At the end of the last installment in this (seemingly never ending) series, I asked for your input as to the content of this chapter. (For those of you who have stumbled into this section of HTINews for the first time, you may want to back up and review parts 1 through 4, otherwise, this one won’t make a lot of sense.Editors Note: These articles are compiled in our Article Library) I have been promising to do an entire chapter on “X-10 Three and Four-Way Switch Circuits” but I seem to be having a lot of trouble finishing up “complex coupling”. At the end of the last section, I again asked you to vote:
Which One Should I Use, Part V
(Dim/Bright Commands and Coupler-Repeaters) Or Which One Should I Use, Part V
(Three and Four-Way Switch Circuits)

I received a lot of emails (which tells me a lot of you are reading this stuff). Just to point out a few:

DIY Home Automation at SmartHomeUSA
From DKJ2@msn.com (David Jahn), “Don’t disappoint, write about Dim/Bright commands, couplers – repeater’s. You can write about three and four way switch circuit’s next!”

From dicklb@spiretech.com (Richard Lee-Berman), “It has been very interesting reading your articles […]It would be great to hear more about dimming […].”

And finally from DaveW3616@aol.com (Dave Weatherwax), who wrote, “I love your writing style. I wish I could sit in one of your classes. [… I ] vote for finishing the repeater article.”

(Dave must think I pay people who send me nice emails. Sorry Dave.)

Anyway, most of you really have no idea if I am just quoting the “repeater” voters and ignoring the “3 & 4-way” voters but please trust me, I am an honest guy. The votes were overwhelmingly in favor of continuing the coupling exposé. Therefore, on to the next segment:

Which One Should I Use, Part V:
(Dim/Bright Commands and Coupler-Repeaters
…plus some other information about new stuff in the world of X-10)

When last we met, our hero, “Captain Coupling” had just won the battle of using multiple repeaters in a house, but that cliffhanger episode came to an end just as he was ambushed by the sinister “Dim/Bright” problem. The curtain opens and we see our hero contemplating this riddle….

Before we talk about “Dim/Bright” commands and their relation to repeaters, we need to be sure we understand the basic of X-10 dimming. When an X-10 compatible transmitter sends out “A1, A1, A-On, A-On” it doesn’t matter how many times the X-10 dimmer receiver receives the “A-On” command. If it receives it once or twice, it doesn’t matter because it can’t get anymore “On” than “On”. Even if it received 32 “A-On” commands, it still would not be any more “On”. That is not the same, however, when considering “Dim” and “Bright” commands. It certainly does matter how many of “those” commands are received.

There are about 16 dim levels in most X-10 compatible dimmer receivers. (Yes, there are some companies like “PCS: Powerline Control Systems” who make some very nice dimmers that have “micro-dimming” but since time is short, I won’t go into that.) If a standard X-10 dimmer receives 2 “contiguous” (that means “touching each other”) dim commands, it will drop down one dim step (about one-sixteenth in brightness). But if it receives only one dim command, then nothing, then another dim command, it will “not” drop down that same one sixteenth. Instead, the brightness of the incandescent lamp drops down an imperceptible amount (about 1/128th).

The early Pico engineers never considered that a receiver might get its commands from something other than the original signal directly from a nearby transmitter. Today, however, it is common for large residential installations (and nearly all industrial and commercial jobs) to have either a coupler repeater made by X-10 (sold through Leviton as their 6201) or from my company, ACT (our part numbers of CR230, CR231, CR130, CR131, plus 4 others). When an X-10 signal is “repeated” by a coupler/repeater, (Figure 1) most commands are accepted by the receivers just as if they had been directly from the transmitter. Even as larger systems came to be, there was seldom a problem. Dimming was usually done either directly from the receiver itself or from a nearby transmitter that happened to be on the same leg (sometimes even on the same circuit) of the home’s electrical distribution system so that enough of the original signal made it to the dimmer receiver that it still got the “contiguous” dim commands.

The problem came to light when larger installations were relying only on the “repeated” signals to do the job. Older repeaters continued to “repeat” the frames of data in the same way as before. In Figure 2, you can begin to see the problem. Whenever the transmitter sends four frames of “Dim”, the receiver only gets two. Plus those two aren’t even contiguous. If you hold your finger down on the “dim” button for a longer time, lets say for almost six seconds, the transmitter may send out 32 dim frames. Any nearby dimmer that receives that original data will go from 100% brightness to 0% in less than four seconds. Your transmitter continues to send “Dim” commands even though your “nearby” lamp has already dimmed down to nothing. But when you glance over to that other dimmer (the one which can only get its signal from the repeater), it’s still at about 85%. Unless you have very good eyes, you may not even be able to tell that it is dimming at all.

Okay, how do we help this situation? Both X-10 and Advanced Control Technologies improved their respective repeaters but in slightly different ways. First, allow me to explain how X-10 did it?

Most serious X-10 technicians are aware of the “6 zero crossing” rule. That is, whenever a transmitter is changing from one address to another address, or from an address to a command, or from one command to another command, it must allow for a pause of at least six clear zero crossings (three cycles) before it continues. I usually explain it simply by saying that the receivers need that time to catch their breath. In reality, the lack of signal resets the integrated circuit’s registers so that it will be able to tell the difference from one to the other. If there is no such “clear space”, X-10 dimmer receivers (those manufactured by X-10 themselves) will think that they are just receiving more of whatever they got at first. In other words if you transmit a string of “Dim” frames and then immediately change to a string of “Bright” frames WITHOUT allowing for a gap of 3 cycles, the X-10 dimmer will think that it is just getting more dimming commands and it will continue to dim.

The X-10 engineers took advantage of this “6 zero crossing” rule and made sure that when their newer repeaters received continuous “Dim” or “Bright” data, they would transmit enough signal so that there would never be more than two blank cycles. In other words, the X-10 repeater (sold as the Leviton 6201) does not really repeat continuous “Dim” or “Bright” data but your X-10 dimmer receiver doesn’t really care. It was a clever solution to the problem. The only time this does become a problem is when the dimmer receiver is one manufactured by someone other than X-10. Other companies manufacture “X-10 compatible” dimmer receivers and they may require true “Dim” or “Bright” data to work correctly.

Now let’s talk about the way we did it. (I may be prejudiced but I happen to think we did it better.) Whenever one of our repeaters “receives” a frame of address data (A1, or B5, P12, etc.), it continues to do what it has always done: it “repeats” that same chuck of data during the next 11 cycles, right over the top of the second time the original transmitter is transmitting it again. The same is true of standard commands like “On”, “Off”, “All-Lts-On” and “All-Units-Off”. The difference is when it detects a “Dim” or a “Bright” command. Instead of merely repeating it, the repeater “remembers” what it just repeated and holds that frame of data in its memory. It then “listens” closely to see if your finger is still on the button. (I know I am explaining this in rather simplified terms but I think it is better than using only terms that engineers would understand.)

If your finger is still holding down the button, our repeater will see the first little tiny bit of data that precedes all X-10 commands (as in Figure 3). Knowing that you are still holding down the button, it will again, retransmit the dim data that it was holding. Then it does the whole process again. As long as you hold your finger down on the dim button, our repeater will continue to repeat dim commands. The same is true if you were holding down the “Bright” button, or if your computer-interfaced, intelligent controller (like the JDS TimeCommander) was programmed to send out multiple frames of “Dim” or “Bright” commands. What is repeated by our repeaters are true dim and bright frames of data.

The ACT repeaters are pretty quick. Each of them can decide in less than 2.7 milli-seconds if it has to repeat that “Dim” or “Bright” data again. Our 3-phase repeaters need to do that in order to repeat the entire frame of data on the other two phases. (It’s kind of complicated so what do you say we don’t go there. Okay?) No matter how many frames of original “Dim/Brt” data was originally sent, our repeaters will always be one frame behind. No matter how clever we are, we have not yet been able to design a repeater that knows when you are going to send a dim or bright command before you do it. We’re good, but we’re not that good.

The next time you have a dimming problem in a large installation, you will have a better understanding of what may be causing it. Also based on this information, I hope that you can make a more informed choice on what repeaters to use.


The title of this installment has the phrase “plus some other information about new stuff in the world of X-10” at the end of it. Now is the time to explain what that means. Everyone in the X-10 world is buzzing about the new modules that have hit (or are about to hit) the market. These new dimmer receivers have (among other features) “remembered state dimming”. That means that if they are dimmed down to 50% and then sent an “Off” command, they will “remember” that they were at 50%. The next time you send them an “On” command, they no longer come on at full brightness (100%) like they used to. Now they ramp up to 50%. Pretty cool! For every one of us who were blinded going to the bathroom at 2 o’clock in the morning, we thank you. But that’s not all. These new dimmer receivers also have “preset dimming” and therein lies the problem. Even though there had long existed a “Preset Dim” command in the standard X-10 command set, the X-10 engineers decided to not to use it.

That choice seemed to most of us to be a confusing one. Those companies that make intelligent front-end controllers had long ago included the existing “Preset Dim” commands in their repertoire. Before X-10 made their dimmers with “preset” capabilities, other companies had already built their own “compatible” dimmers that did use the old commands. Interestingly, there are even X-10 compatible thermostats that use the old “Preset Dim” commands for temperature set-back. Now X-10 was building new dimmer receivers that did not use these old commands. Instead, they use a new set of commands using “extended data”. This decision caused ripples in the X-10 industry that have yet to settle down. Most of the front-end controller guys have now included (or are struggling to include) these new “Preset Dim” commands into their systems. One down, one to go.

Then X-10 introduced their new modules with “two-way” capability. What is two-way? That question is not as simple as you may think. Ask four or five people and you may get four or five different answers. Two-way communication is inherent in most forms of communications today. When you talk on the telephone you can also listen to what the other person is saying. You are using your computer modem right now to read this file on the HomeToys web site. You send commands from your modem to this web site and in turn, this web site sends this file to your modem (through a myriad of other computer systems, of course). All of the newer powerline communication protocols (Intellon, LonTalk, etc.) also have “two-way” communications. Instead of simply “transmitters and receivers” they have “nodes” and each node is a transceiver capable of both sending and receiving data.

Sometimes “one-way” communication is preferred. When I listen to my favorite “oldies” station on my car radio, the signal is going from the radio station to my car radio. But it would be inappropriate and impractical for every car radio to also be able to transmit back some information to that radio stations. Until recently, X-10 systems were just like that. Transmitters transmitted and receivers received.

Sophisticated communications protocols require complex duplex (two-way) capabilities because decisions can be made at many different locations. In the case of some of the newer powerline communications, the system itself has what is called “distributed intelligence”. That means that there is no one central location in which decisions are made. Since all the parts must work together and each may have a say in the decision making, each part (or node) must be able to both transmit and receive data.

I have often found myself in conversations where someone would be promoting the need for all X-10 devices to have two-way capability. Most of the time they would advocate this upgrade without fully understanding the true nature of it (or the cost). They may erroneously think that the simple addition of two-way capability would immediately solve their perceived problem of X-10 unreliability. Buzz, wrong! Let’s say that your front-end computerized intelligent controller was scheduled to send out an “A1, A1, A-On, A-On” command at a particular time of day. A few minutes later, it was also supposed to send out an “A1, A1, A-Status-Request, A-Status-Request”. If it fails to get a response, what does that prove? Surprising it actually proves nothing. Current X-10 systems, even in very large, multiple transformer, multiple building systems, usually work very well. They do this because professional, trained and experienced designers and installers did all the right things to make sure that the signal gets to all the receivers. In poorly designed systems, unreliability has more to do with signal strength and noise levels than it does with the lack of two-way communications.

Please don’t misunderstand me. I am not saying that the addition of two-way capability is a bad thing. There are several situations where it would be of great advantage. Let’s say that your front-end computerized intelligent controller was scheduled to send out an “A1, A1, A-On, A-On” command to a wall-mounted receiver at a particular time of day. A few minutes later, a human being over rides that command by pressing the button on that receiver, turning it back off. A moment later, with its new two-way capability, that receiver will be able to send out that information by transmitting “A1, A1, A-Status-Off, A-Status-Off”. Your front-end computerized intelligent controller now knows that the receiver is off. Now that is an appropriate use of two-way. Everything, however, comes at a cost.

We at ACT were aware that some of the extended code data sent by these new modules may be a problem for our repeaters but we were not sure just how much of a problem it would be. ACT and X-10 have been close partners since 1989. In the X-10 world, only 2 companies make repeaters. Obviously, X-10 Ltd. is one of them, making the 6201 for Leviton. We at ACT currently make eight different X-10 compatible repeaters: two different ones for 120/240v split-single phase distributions systems, two for 120/208v 3-phase systems, two for 277/480v systems, one for Canadian 347/600v systems and even one for 240/415v, 50Hz distribution systems (only for export).

We have sold a lot of repeaters over the years and one of our top sellers has been our CR230, residential unit (Figure 4). I would doubt that there are many residential customers who give more than a passing thought about the other functions of our more sophisticated repeaters. While X-10 has long had the “extended code” possibility in their protocol, we at ACT patented our own extended code (February 1996) increasing the 256 address capability of the standard X-10 to our own having 4,096 addresses. This new “ACT Code” was done for those commercial customers who wanted a secure system that could not be circumvented by anyone with a standard X-10 transmitter.

In order to standardize our manufacturing, all of our repeaters have long had the ability to recognize both the standard (256 address) X-10 protocol, plus our own (4,096 address) ACT code protocol. The problem is that now that X-10 has expanded on its use of its own extended code data, we find that our repeaters erroneously recognize those signals as being the “ACT code”. Our repeaters shift into their second mode. Unfortunately, our protocol is different enough that true frame repeating of the X-10 extended code does not work. When one of the new two-way modules is plugged in for the first time, it transmits an “I’m Here” message. Unfortunately, our repeaters do not understand this new “I’m Here” data and things start going wrong. In other words, our repeaters think that they are repeating ACT’s protocol and in doing so causes the new Leviton two-way modules to re-transmit their initial “I’m Here” message, over and over again.

While the CR230 is our least complicated repeater, most of our other units (Figure 5) have 8 dip-switches and additional features to afford system designers many options for complex coupling situations. One of those dip-switches is labeled “Extended Code Only” [up] or “Both Codes” [down]. While those industrial customers who have ACT’s “4,096 address” equipment in place know what that switch means, it is easily misunderstood by other customers who have only heard of X-10’s new extended code.

It appears that the Leviton 6201 also has a problem. Unlike ACT’s repeaters, it does not even try to repeat the new extended data. Like other companies who manufacture X-10 compatible products, we at ACT will also adapt our equipment to take advantage of the new commands. We have already begun making our plans to re-write our repeater software to recognize X-10’s extended code. Since the project has just begun I can’t yet report a solution, but keep your eye on this web site and our own ACT web site ( www.act-solutions.com ). As soon as we have new IC chips available I will let you know.

Sadly, we have come to the end of this episode in our continuing saga of “Captain Coupling” and not surprisingly there seems to be another cliffhanger ending. How will we ACT deal with the new X-10 codes? What will become of “Captain Coupling” and his faithful companion, Phil? And what will be the title of the next episode? Will it finally be….

Which One Should I Use, Part VI
(Three and Four-Way Switch Circuits)

…or will there be more to the “Repeaters vs. the X-10 Extended Code” story. Stay tuned…..

Oh, I almost forgot. Last time I asked that you send me any interesting email signatures. I am often amused by the variety and wit some people show at the end of their emails and newsgroup posts. I mentally collect them because they make me smile and sometimes they make me think. Here are a few (of the clean ones) that readers sent me. Some of them have a distinct Star Trek theme. Some of them are just weird and then there are some that defy explanation.

Excuse me. What does God need with a Starship?

CAUTION: Don’t look into laser beam with remaining eye.

I want to be what I was, when I wanted to be what I am now.

I didn’t say that I didn’t say it, I said that I didn’t say that I said it!

Only those that truly dare, truly live!!!

Life is just a computer simulation.

“Don’t speak unless you can improve on the silence.” -Spanish proverb

What if there were no hypothetical situations?

What a relief. Look ma, no hands. As a shapeshifter, I can say this for real. Odo out.

I smell bacon, I smell pork. Run little piggy. I have a fork.

As always, comments and suggestions are always welcome. Email me at actpccpek@aol.com