From: v087mxgb@ubvmsb.cc.buffalo.edu (Shawn E Thompson)
Newsgroups: rec.autos.tech
Subject: unofficial FAQ-type info on car alarms...
Date: 26 Aug 92 15:21:00 GMT
Organization: University at Buffalo
News-Software: VAX/VMS VNEWS 1.41


Hi all,

a new net-friend asked for some alarm info. I am presently
installing my fourth alarm, I've done some simple electronic
design work on an alarm, and I've worked with professionally
installed alarms. I'm also an Engineer (mostly in the auto 
industry, but presently sidetracked in another field). So,
I geuss I thought I could share some alarm info I might have.


It's not real well organized, just some notes as they came
to mind. I'm not affiliated with any companies named, I just
used them as examples. 



ALARM STYLES:

	Ignition key - alarm is wired directly to ignition and 
	automatically arms and dis-arms via ignition key. A
	delay is employed to allow the driver to get in & out.

		PROS: no remote to lose, no code to remember
		CONS: a thief who breaks ignition lock (most
		      common method of auto theft) disarms it

	Keypad - similar to above but uses a secret id number
	(similar to a bank-card) instead of or in conjunction
	with the ignition key. Also uses delay to allow driver
	to enter and exit.

		PROS: no remote to lose, can't be disabled by 
		      beaking ignition lock
		CONS: code to remember, keypad must be mounted 
		      somewhere

	Remote control - uses a remote, key-chain transmitter
	(similar to a miniature garage door opener) to arm
	and disarm alarm.

		PROS: no keypad to mount, no codes to remember,
		      cannot be disarmed by breaking ignition
	              lock.

		CONS: if keychain is lost, car can be found by
		      pressing remote.


SIRENS:

	Electronic - uses digital circuitry to create loud alarm 
		     sound. Very distinctive auto-alarm sound.

	Motor driven - electric motor rotates siren, sounds like
		     air-raid siren. Generally more durable, but not 
		     quite as loud. Usually more expensive.

ACCESSORIES:


	Shock sensor - device that detects high-impulse vibration
		     (hitting car or window) and sets off alarm
		     instantly.

	Motion detector - device that detects low-frequency vibration
		     (towing or jacking) and sets off alarm instantly.

	Glass breakage sensor - similar to shock sensor, but uses
		     a microphone with a discriminator circuit to
		     "hear" frequencies of glass breaking, and sets
		     off alarm instantly.

	Ignition cut off - disables the starter or ignition (spark
		     to spark plugs) while alarm is armed.

	Pager - device that beeps a pocket pager when siren is sounded.

	Intrusion sensor - ultrasonic detector (similar to automatic
		      door openers in department stores) that looks
                      for a change in reflected sounds waves. Ideal for
                      convertibles since top can be cut or left open.

	Voice warning - gimmick that speaks a warning over a loudspeaker
	              when alarm is about to go off. Usually says
                      something like " you are too close to the car
                      please move away".


MISCELLANEOUS:

	Wheel locks - cost about $10-$12 on sale (worth their weight
                      in gold, especially if you have nice wheels).
                      Insist on McGard brand (there *is* a difference
                      in quality and support).

	Hood lock - probably the best device on the market (Chapman
                      brand comes to mind). This is a *heavy* duty
                      cable that locks the hood *and* disables the
                      ignition. Noone can open your hood, and noone
                      can hot-wire your car from inside.	

	Steering wheel locks - "The club", etc - very visible devices 
		      that lock the steering wheel to the brake
                      pedal. Several versions available: some lock 
                      the brake pedal up, some lock it down, some
                      just clamp onto steering wheel to impede 
		      steering. My thoughts are the kind that lock 
		      the brakes ON and hold the steering wheel are
                      best (they squeeze between the pedal and steering
		      wheel) since they inhibit towing also. Be careful
                      with a titl-wheel that the steering wheel is 
	 	      tilted properly so a thief can't just un-tilt 
		      the wheel and remove the club.

	Locking gas caps - obvious.

	High security trunk locks - very popular in NYC. Virtually
                      theft-proof replacement lock for trunk lid. 
		      Mounting plate looks a little goofy though.



NOTES:

	Remote trunk releases are dangerous! Every thief knows what
	cars come with remote trunk releases (and many are in the
	glove box, which doesn't lock). Many people lock valuables
	in their trunk, especially when shopping. Well thieves know
	that and (especially during Christmas shopping season) can
	just break one window, pop open the trunk, grab the goods,
	and be gone in (literally) *seconds*.

	Most alarm accessories are ground-switch activated, meaning
	when you ground the instant on trigger input (wire) the alarm
	is tripped instantly. Most accessories are just switches that
	you place between this wire and ground. For example, my alarm
	has an instant on trigger wire that is blue. When this gets 
	grounded the alarm sounds for two minutes. I hook the shock 
	sensor between this wire and ground. When the car is hit, the
	sensor closes its switch, grounding this blue wire and tripping
	the alarm.

	Current sensing alarms trip when a light (dome light, trunk
	light etc) goes on. These have to be isolated from some
        accessory circuits (like electric engine-cooling fans) which
        turn on by themselves.

	Hardwired alarms use switches on the doors and trunk to
	ground a wire and set off alarm.

	Most alarms are a combination of the above two types.


	Alarms are *just* noise makers that are intended to draw 
	attention and scare off thieves/vandals. A simple alarm 
	is as good as a complex alarm. But for real security you
	need a hood lock, wheel locks, gas cap lock, and ignition
	disabler.


	I reccomend a simple current-sensing remote alarm from 
	JC Whitney for as little as $49 ( a little more $ with 
	hardwire options if you don't have courtesy lights in 
	trunk or hood). These can be as simple as *1* wire to 
	connect and doing it yourself can save HUNDREDS of dollars. 
	Complex alarms can have 10-12 wires to route and connect 
	and, if you're not handy, need a pro to install. Definitely 
	get a hood lock, ignition disabler, wheel locks, and gas-cap 
	lock (I bought all this	for under $100 at my local custom car 
	store (wheel locks and locking gas cap) and JC Whitney 
	(simple alarm and hood lock).



Shawn E. Thompson                         | Project Engineer/Mgr  (716)891-3375
v087mxgb@ubvms.cc.buffalo.edu             | Leica, Incorporated
University @ Buffalo                      | PO Box 123
Graduate School of Mechanical Engineering | Buffalo, NY 14240-0123
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