Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.2 9/18/84; site ucla-cs.ARPA Path: utzoo!linus!decvax!ittatc!dcdwest!sdcsvax!sdcrdcf!ucla-cs!wales From: wales@ucla-cs.UUCP Newsgroups: net.auto.tech Subject: Motion sensors in car alarms Message-ID: <8927@ucla-cs.ARPA> Date: Wed, 12-Feb-86 22:15:38 EST Article-I.D.: ucla-cs.8927 Posted: Wed Feb 12 22:15:38 1986 Date-Received: Fri, 14-Feb-86 07:20:57 EST Reply-To: wales@ucla-cs.UUCP (Rich Wales) Distribution: net Organization: UCLA Computer Science Department Lines: 59 Most automobile alarm systems today seem to include a "motion" or "impact" sensor -- either a simple weighted spring, or a sophisticated electronic device -- which sets off the alarm if the car is hit or jarred (as, for example, during an attempted tow). I seriously question whether these sensors are really useful. I tend to think they are more trouble than they are worth. I would appreciate any comments on the following ideas: ==> A motion/impact sensor can tell whether someone has bumped into your car. If you return to your car and see that the alarm has not been set off, you know you needn't inspect it carefully for damage. On the other hand, I would think that an alarm would tend to scare the "hitter" away -- where otherwise he might (and I repeat *might*) leave a note. In such a situation, the alarm would be counterpro- ductive. As far as alerting the car owner so that he can go out to his car and possibly identify the other car before it leaves the scene, I doubt this would work unless the owner could get out to his car within a few seconds at most. ==> A motion/impact sensor can set off the alarm if someone tries to tow your car away. On the other hand, a thief who is brazen enough to tow away a car is not likely to be deterred by an alarm. (Some people may use this point as an argument against *all* alarms, of course.) Besides, just because a car being towed has an alarm sounding off doesn't mean the car is being stolen (maybe it was parked illegally and is being towed legitimately). So, neighbors or passers-by may not necessarily take any action (except to curse the racket being produced by the alarm). I think a much more effective measure to discourage illegal towaways would be to engrave the VIN number all over the car (so as to make it less attractive to the "chop shops"). ==> Motion/impact sensors contribute heavily to false alarms (especially with cars in parking structures), thus fostering a "cry wolf" image and eroding public willingness to take car alarms seriously. What do other people on the net feel about motion/impact sensors? Since I know the subject of car alarms is almost a "religious" issue, let me emphasize that I am asking specifically for opinions about motion/impact sensors -- not car alarms in general. If you do feel impelled to speak to the general issue of whether car alarms are worth having, go ahead (how could I stop you, anyway? :-}), but *please* be sure to change the "Subject:" line in your followup. -- Rich Wales // UCLA Computer Science Department // +1 213-825-5683 3531 Boelter Hall // Los Angeles, California 90024 // USA ARPA: wales@LOCUS.UCLA.EDU -or- wales@UCLA-LOCUS.ARPA UUCP: ...!(ucbvax,ihnp4)!ucla-cs!wales