I have two of the radios, 40 channel with all controls in the microphone.
The power connection and the antenna connection are obvious and easy. There is also a six-position connector that must do something besides just feed a speaker.
SoI am seeking information about this particular model radio: RCB40. At least that is given as the FCC ID, and there does not seem to be any other markings, inside or outside.
Tracing the internal circuit can be done, but as the radio consists of a number of circuit boards soldered int a main board, that will take some serious effort, and there is a risk of causing damage by unsoldering and resoldering.

 

You can try

Email us at hello@robertsradio.com

Looks like they went out of the CB business and being a British Company very little documentation to be found on any of their products. You can still buy them NIB on eBay for ~30USD plus shipping. If all you need is an operating/installation manual maybe someone would be kind enough to copy it for you.

Good luck!

 

I looked inside the boxes and they are built more rugged than most radios. The tag states "made in Japan" but it is obviously a British design. Not sure why I have two of them, it was evidently a while ago, and they were "rather buried", probably because at the time I could not get any information. In my current vehicle there is no place to install a radio so that it can be operated, but with everything on the microphone And a long cable mike connection they can be well out of the way.
I did locate them on one website but all of the information there was that they are 40 channel AM radios that run on 13.5 volts. If Roberts made a car radio or stereo, they may have had a scheme for muting the radio. That was not mentioned.

My hope is that somebody, some place in the world, had one and can recall what that cable connected to.

 

From what I saw, they were designed for the main body to be located in the trunk and controlled by the mike unit. Roberts apparently did and still does make audio gear and the CB was somehow supposed to integrate with the car audio system speakers. Could even be where the CB breaks and mutes the stereo output to use the car speakers for audio. Real oddball stuff.

 

From what I saw, they were designed for the main body to be located in the trunk and controlled by the mike unit. Roberts apparently did and still does make audio gear and the was somehow supposed to integrate with the car audio system speakers. Could even be where the CB breaks and mutes the stereo output. Real oddball stuff.

Certainly it is odd, a mother board and about five modules, for of them well shielded, mounted edgewise up from that board. And lots of multi-pin connectors tying the wire harness to many locations on the motherboard. most CB radios just solder the wires into the PCB and forget about ever servicing it. Not like good military surplus, but certainly made worth repairing. I had not thought about that cable being for muting the music, but that is a possibility. The mic does have a volume control and a squelch control, plus the 2 digit channel display , TX and RX indicators, and the power switch on the volume control.

Probably I should connect an antenna power it up, and see what it does. It might be a good surprise and work as it stands.
Or maybe not.

 

You might have better luck opening the handheld unit and trace the wires.

 

The handheld part is not where I have the questions or need to know more. Plus, the handheld cable goes through a very small 20 pin connector and then the cable enters the case and all those wires are terminated in a feed-thru board with RF filters. And then the wires from THAT board go to a bunch of different connectors that plug into the motherboard.
Besides that, what I need to know is the connections to the other connector, a six position connector that has a shielded cable. Those wires also go to that feed-thru board. So any tracing of wires will be a major effort.
Somebody who has had one of these radios will know what that connector was for, and that alone will be a very big help. That is why I posted here, because there are a lot of people who know a whole lot about a whole lot of things, and are willing to share their knowledge.

 

Have you seen this? RCBE-04 Microphone Extension Module. Not much to go on...

Also...

 

That is the one. Thank You INDEED!!
The second cable/connector does not appear in that installation drawing, so no clue there.
Where did you find that picture?? The shape of the radio enclosure is much closer to square than what shows in the picture.
Or is it on your shelf? Do you have any literature that came with your radio??
I have not tried to contact any of the Ebay sellers because I don't need another radio. two of these is plenty, so far.

 

First is from eBay listing roberts rcb-40: Search Result | eBay
Second from RigPix Database - CB, "Freeband" and more - Roberts RCB-40

Grasping at straws as there is very little info available...

 

I had not followed that ebay link, but as the listing is from Spain I was reluctant to chase it. I had already seen the "RigPix" posting. Not much information there.
Even the sites that tout having every manual for everything are rather bare. Not to mention very expensive. So I guess that it will come to powering up with an antenna connected and a speaker plugged in and seeing what I get.

From the size of that microphone package it seems like it may also include a speaker. That is far from my favorite arrangement.

Perhaps I should contact the seller in Spain and see what they would charge for a copy of at least part of the manual. Or see if they are intersted in purchasing two more of those radios.