All of my cars just have the standard keys that lock the doors and are needed to start the car , as well as release the steering lock .
I detest noisy car alarms which go off when you don't want them to and are generally ignored anyway since this is so commonplace .
If I am going away , and want to immobilise any cars , the newer ones with electric fuel pumps can be safeguarded by pulling the fuel pump relays ; older cars with mechanical pumps by unclipping the distributor cap and removing the rotor arms .
Most of the older models had Scorpion alarm systems fitted by the supplying dealer when insurance companies began asking for more security in the early 90's. Problem was that no two systems would be exactly the same in terms of installation/ sensors/ alarm/vehicle immobilisation and so were problematical to trouble shoot. Many of these systems are breaking down now simply because their installation was " less than optimal" with Scotchlock connectors etc. Because many of these cars are now being run at the "budget end" of the market when these alarms go faulty they are often disabled or removed altogether. After the mid 90's Mercedes incorporated their own security system into the cars wiring and these don't seem to give the same problems- if they do they have a standard layout and more easily repaired replaced. The security was also improved by coding many of the electronic components together so that the ignition switch was linked to the engine ECU for example.
ps Scorpion alarms are resurrected here http://www.scorpionauto.com/ and there are some guys there who are familiar with the old Merc systems if you wanted to pick their brains?
Yes , I have had these Scorpion units on at least two of my cars . I have always carefully removed them to leave no trace .
One of my W124's had the factory fitted alarm , designated by a little red dot on the keys , it was completely invisible in it's operation and fitting - I only once set it off when I noticed the bonnet wasn't properly closed , and lifted it after having first locked the car .
My '81 SL has a Laser full alarm immobiliser fitted with central locking interface. I ripped out the crap vacuum system and replaced the door and boot elements with electric ones. Fed the cables down the old vacuum pipes so no disruption.
Full remote central locking with remote boot access. Cool