back buffer, relevant only if <CODE>Mode</CODE> is a refinement of <A HREF="../guide/modes.html#input"><CODE>input</CODE></TD>
    </TR>
</TABLE>

<P>
    An instance of a Filter or Device type <CODE>T</CODE> which is not <A HREF="../../../../doc/html/CopyConstructible.html"  TARGET="_top">CopyConstructible</A> may be appended to the chain in one of two ways:
</P>
<UL>
    <LI>by using a <A HREF="../../../../doc/html/ref.html" TARGET="_top">reference wrapper</A>, or 
    <LI>if <CODE>T</CODE> is a standard 