%%% The supervisor
%%% maintains bussy variable
%%% calls decission if no longer bussy.
%%% always scheduled
S1  TRIP    Receive,Arrival,0	After the first arrival, 
    SET	    bussy,on		the elevator stays bussy,
    PUSHJ   $0,Log:E9 %%hide
1H  SET	    $0,300		until after 300 units
    TRIP    Expect,Arrival,$0   pass by
    BNZ	    $255,1B		with no further arrival.
    SET	    bussy,off		It's no longer bussy, 
    PUSHJ   $0,Log:E9 %%hide
    PUSHJ   $0,Decision		a decision is forced,
    JMP	    S1			and the coroutine starts over.
%%off