Car Alarms: UNGO Alarm, ungo car alarm, starter wire

Question
I have a 1974 Jaguar xke.  I bought it used and it came with an UNGO car alarm.  I assume it's from the 1970s.  It does not have a remote.  It has an alarm code and a disarm code.  The front of the box in the car has a 4 digit number code dial that sets the code.

I have a battery shut off switch and when I turn it on the horn goes off and  the car won't start.  I do not see a valet switch.  How do I disarm the UNGO system?  I switch the battery on and the horn goes off.  I immediately hit a red button on the front of the UNGO box, but nothing happens.  What else might I do to turn the unit off?

Thank you.

Answer
I would strongly suggest upgrading that system to something newer.  If you just want to remove the system here is a generic how to:

Typically an alarm system would be installed on the driver's side interior of the vehicle.  This system would have been tapped into the ignition switch wiring running down from the key.  If you remove the dash panel(s) under the steering column you should be able to locate where the harness was added that goes to the alarm.  Disconnect each wire that was tapped in and insulate the factory wiring.  You will also see that at least one of the wires was cut, this is the vehicle starter wire that runs from the key to the starter.  This wire needs to be restored, I always recommend soldering all connections but crimp connectors should also work.  Make sure that you remove all connections to the alarm and that any wires that may be exposed are insulated and mounted in a way that they will not interfere with any moving parts and do not run the risk of shorting out.  Remember to take your time and follow each connection running from the brain of the system, leaving one wire connected that you are unsure of the function could cause problems in the future so be sure to remove every wire.