Rule 424(b)(3) File No. 333-77295 PROSPECTUS SUPPLEMENT Protection One Alarm Monitoring, Inc. 818 S. Kansas Avenue Topeka, Kansas 66612 May 1, 2001 Re: Offer to Exchange Registered Series B 8 1/8% Senior Subordinated Notes due 2009 for Any and All Outstanding 8 1/8% Senior Subordinated Notes due 2009 ----------------------------------------------------- Dear Investor: Please note the following change to the Prospectus dated April 27, 2001 relating to the above-referenced offering. On page 8, the text next to the heading "Maturity Date" is replaced in its entirety with the following: "January 15, 2009." PROTECTION ONE ALARM MONITORING, INC.