specification ALTERNATING_BIT_SERVICE [PUT, GET] : noexit 

library TYPES endlib

behaviour

   SERVICE [PUT, GET]

where

(*---------------------------------------------------------------------------*)

   process SERVICE [PUT, GET] : noexit :=
      PUT ?M:MSG;  (* obtention of a message *)
         GET !M;   (* delivery of the message *)
            SERVICE [PUT, GET]
   endproc

(*---------------------------------------------------------------------------*)

endspec