I recently purchased a system from "Ocean Technology
Systems" (OTS).  It is called the "Buddy Phone".  All you do is
take off the mouth piece from your second stage and replace
it with the special buddy phone mouth cup which contains a
microphone.   You will also need the surface unit. This is a
multi channel portable surface station.  The station has a
female RCA receptable, for connection to any type of
recording system.  It has a "Mic Level" output.

Each diver unit has ear phone and microphone and runs for
about $400-$600 (US dollars)

The surface unit about $1,000 (US Dollars)

System is called the Buddy Phone STX-100.

You can also use the Aquacom (SSB-2001) single sideband
acoustic telephone if you are using full face AGA masks.

I have had great luck with these units. 

Ocean Technology Systems are in Costa Mesa California, USA.
 Phone:  (714) 754-7848
 FAX:  (714) 966-1639

They may have distributors in Europe, but I do not know them.
They may even have a web site.

Good Diving,

Ken Potts

