This may help https://www.beoworld.org/beotech/mcl3082a.htm Stoobie

That does give a lot of useful info thanks.  What I can't figure out is how it actually connects to the Beogram 3000 - how does the receiver get the instruction from the mCL30?  There is no specific connection for it on the back of the Beomaster 3000, and there is no mention of the MCL30 in the Beomaster 3000 user manual. Mind you, they can be bought quite inexpensively; I'll probably just buy it anyway and try to figure it out.

According to the Beotech page linked to earlier in this thread the MCL30 is simply and on/off button ( or mute if you will) for the speakers connected to it Login to view image So the operation of volume and channel switching etc. Will have to be done on the BM3000.

It's a little confusing; in the table of functions, under 'What may be operated?', it says 'All Beomaster Terminal functions', giving the impression that anything you can do on the Terminal 3000 remote can be done through the MCL30. I'm still at a loss at how the damned thing actually connects to the Beomaster 3000, since the Beomaster 3000 seems to have no specific connection for it.  I am guessing the added the MCL30 to the range of products after the Beomaster 3000 was released, as the Beomaster 3000 manual makes no mention of it's existence. Thanks for your help thoigh - I know more now that I knew earlier...

I found the diagram for the BM3000 and I can see that the speaker connectors (both speaker 1 and 2) are three pin connector where the third pin for the right speaker carries 5V power and the third pin for the left speaker carries a data signal. So probably the remote control can operate the BM3000 via the tranceivers IR eye. The other text I linked to before might just describe the function of the button on the transceiver which the does have a very limited functionality, especially if the BM3000 is not on.

On all MCL products the datalink is on the 3rd pin of the speaker socket. Login to view image

My memory is a bit hazy on this now,as I only ever saw a couple of them It did indeed extend the operation to another room,including remote control. The oversight in the design seemed to be though,that you needed to switch the second pair of 'speakers on/off via the transceiver manually,and could'nt ever have just the remote room 'speaker operating. We used to get around this by reversing the speaker 1/2 connections,as the sockets are cabled in paralel.Speaker 1 (main)then can be switched off via the  2 switch under the cover. You'd need to wire up the MCL30 using the special cable and connections as per Keith's post above.The cable and special 3 pin plug's are becoming very rare now though. If you are looking to upgrade ,it might be worth looking for a Beomaster 3300,as these were fully MCL 2(Extra Speaker etc) system compatible. Nick

Thanks everyone for all the advice on this.  I had considered the 3300 but it would not match my existing Beocord 2000, Beogram 3000 and Beogram CDX.  The 3300 range got itself a bit more of a 1980s look which I'm not as keen on!  The 2000 and 3000 range are much nicer to look at, and I've looked at the other items in the 3300 range on ebay (cassette, turntable, cd plaver); it would be expensive to get the matching set. I think therefore I've just made the decision to keep what I've got.  It looks great and it sounds great, and I can live without the remote!  As for the speakers, I think I'll by an external speaker selector so I can switch between speakers 1, 2, or both.