A visitor asked me for more clarification about the function performed by a “Shift” button on an aftermarket alarm system remote.
Some aftermarket alarm systems were designed so that you can put the same system in two different vehicles and control both of them from a single remote transmitter. Selected systems from Alpine, Autopage, DEI and Omega offer this capability. The remote facilitates this by changing one piece of information encoded in the signal when the shift button is pressed. Essentially, the shift button is an A-B switch. One vehicle recognizes the signal transmitted by the remote when it is set to A and the other vehicle recognizes the signal when it is set to B.