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[pomonabill221]

What is the C all about? 

[dhouston]

For the record, the 751 does have an FCC id.

Thanks.

My guess is that the noisy lamp was outputting enough RF EMI to affect the 6' distant super-regenerative RF receiver in the TM751. That would explain why the relay did not respond to RF and noise on the powerline explains why the PLC signals did not get through.

It could also be that the noise on the powerline was of sufficient amplitude to directly affect the super-regenerative receiver. A few years back, there was a frequent problem which I dubbed "endless dim syndrome" wherein TM751s would send Dims continuously due to inductive coupling of the 120kHz powerline bursts to the super-regen receiver - something similar might explain this.

[dhouston]

I found a real old TM751 and it did have a FCC ID number on it. My Date Code 08D14 has no FCC ID but has the relay in it. Also has the small receiver board in it like the CM15A.

Now to confuse things even more. 

I have one with a 9K48 datecode that has a super-regen receiver and FCC ID. So it looks like the datecode is not a reliable indicator. The FCC ID, however, should be a reliable indicator of the type of receiver.

A further complication is that the main board was also redesigned. The older version only supplied +19V to the RF daughterboard which had an LM7805 linear regulator onboard. The newer RF daughterboard used in the CM15A needs +5V.

[Noam]

Well, it looks like they *sort of* changed the model numbers.
Apparently (and I saw this on a sales site online, not direct from X10), the TM751A is the one with the pass-through outlet, and the TM751C is the one with the 15A controlled outlet.

It would have been nice to see them use a different number, but at least the letter at the end is a distinction of some sort.

I'm not sure why they would keep manufacturing a transceiver that is "deaf" to the powerline (although it is a lot cheaper to make), instead of just making more RR501's.

[pomonabill221]

Yes, an RR501 IS polite, and has higher PLC output, but it doesn't do all 16 unit codes.  darn it! 

[dhouston]

Yes, an RR501 IS polite, and has higher PLC output...

Unless something changed with the redesign of the mainboard, the TM751 and RR501 both had 10Vpp PLC output.

• http://davehouston.org/x10-sig.htm

Europe limits PLC to ~4Vpp so X10 may have anticipated that the FCC would eventually do the same.

Since X10 has discontinued the RR501, I shelved my plans for the RR5x5 which added a serial interface to it. Instead, I designed a powerline modem with RF receiver and serial interface but I doubt it will ever be for more than my own use as the cost of UL approval is prohibitive.

[pomonabill221]

oopss... sorry about that!  From memory, I thought the 501 had a hot output, and others did not... didn't know about the 751 though..

[dhouston]

Here's a picture of the TM751A with a sticker where the switch was.



There's a large empty area where the relay isn't. The pushbutton (slightly depressed) is hot glued beneath the sticker. As the PCB no longer has On/Off circuitry, it appears they are merely using up cases designed for the older models.

[pomonabill221]

GEEZZZ... they can't even put the sticker on square?!?!?!

[Brian H]

WOW. Does that TM751A look like it has a quick fix patch job on it. I agree the label is not on straight.  

[nabril15]

Brian, the FCC id is b4srr501

[dhouston]

Brian, the FCC id is b4srr501

Whoa! I thought you had a TM751.

[Brian H]

RR501 is the better transceiver.
Has both a RF and Power Line receiver in it. Along with a Power Line Transmitter.
Has a Unit switch for 1 or 9.
The internal appliance type relay in it can be controlled by an RF command or a power line command. The TM751 {if it has the relay} can only be controlled by an RF command and is hard wired to Unit 1.

[nabril15]

thank you all.
After all is said and done, I have a 501 and not a TM751. Everything works fine now.

Sorry for the psychology, but I remain baffled by the fact that people (like yourselves) are willing to spend your time helping others with their x10 issues, yet some misguided psycho is able and willing to go into a theater and injure and kill so many.

THANK YOU ALL.

[dave w]

I remain baffled by the fact that people (like yourselves) are willing to spend your time helping others with their x10 issues, yet some misguided psycho is able and willing to go into a theater and injure and kill so many.

You are baffled by the fact that not everyone is evil?