% This can be used to print letters on AI Lab letterhead on those printers
% which have them in the third tray.  It will also put the extension number
% in the appropriate place at the bottom of the page; due to feeding
% variability in the printer, this may sometimes be off.  Second and
% subsequent pages are printed on standard paper; copy to blank bonded
% paper if you so desire.

% Extension numbers are defined with other personal parameters by the
% declaration
%
%    \extension{xxxx}
%
% Send bug messages to Yishai@OZ.

\makeatletter
\let\@origshipout=\shipout
\def\@testvbox{\vbox}
\def\@aishipout#1#2{%
   \def\@foo{#1}
   \ifx\@foo\@testvbox
       \@origshipout\vbox to 9.19in{\vskip\@origvoffset
                                    \moveright\@orighoffset#1{#2}%
                                    \vss
                                    \hbox{\hskip 4.9in\ninrm\@extension}}
    \else\errmessage{Bug in \string\ailetterhead!}
       \@origshipout#1#2\fi
    \special{tray 1}%
    \voffset=\@origvoffset
    \hoffset=\@orighoffset
    \global\let\shipout=\@origshipout}

\def\ailetterhead{%
 \special{tray 3}
 \xdef\@origvoffset{\the\voffset}
 \xdef\@orighoffset{\the\hoffset}
 \hoffset=0pt
 \voffset=0pt
 \let\shipout=\@aishipout}

\def\@extension{}
\def\extension#1{\def\@extension{#1}}
\makeatother