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From: jww@sdcsvax.UCSD.EDU (Joel West)
Newsgroups: comp.sys.mac
Subject: Re: Blinking Apple
Message-ID: <3701@sdcsvax.UCSD.EDU>
Date: Fri, 21-Aug-87 10:35:08 EDT
Article-I.D.: sdcsvax.3701
Posted: Fri Aug 21 10:35:08 1987
Date-Received: Sun, 23-Aug-87 01:22:47 EDT
References: <1574@crash.CTS.COM>
Organization: Palomar Software, Inc., Vista, CA
Lines: 3

You might check Tech Note #85 "GetNextEvent; Blinking Apple Menu".
The GetNextEvent filter routine pointed to by memory location
$29A sets the blinking.