Hi and welcome to the site.
I don't know what sort of alarm your car has; mine has a Sigma M30 which has this process listed;
The Sigma M30 alarm system has many more features than you may be aware of. The standard Subaru fitted system has the majority of these features switched off for simplicity and to conform to European legislation. Just to let you know what can be done……..
User Features
The following features are switchable by the end user, using the keypad, and are detailed in the back of your operating instructions.
To access this mode - turn on the vehicle ignition, press the remote button once, type one of the numbers listed in the chart below, immediately turn off the ignition. The numbers will have the following effect:
Number
Function
0
Last trigger isolation - allows the system to be set excluding any circuit giving a trigger signal at the end of the settle time (i.e. allows the system to be set with a defective bonnet switch, without “false alarming” until the switch can be replaced)
1
Turns off the bleeps only for the next time the system is armed (If bleeps turned on!)
2
Turn off ultrasonics only for the next time the system is armed (also possible by pressing the Remote Key with the ignition on before arming)
3
Puts the system into valet mode (effectively freezing the passive immobilisation and any other features such as auto arm when the vehicle goes in for service. System re-activated by arming with the remote key).
4
Turn on auto-lock (an anti-hijack feature that locks the doors and boot when the ignition is turned on)
5
Turn off auto-lock
6
Turn off bleeps every time system is armed or disarmed
(Turned off at manufacture to comply with legislation)
7
Turn on bleeps every time system is armed or disarmed
( Note: This will contravene current legislation)
8
Displays vehicle’s battery voltage – 10 flashes on dashboard LED = approximately 10 volts
9
Turn on super-lock for next set period (allows the alarm to arm, but then shuts down the receiver. This reduces the systems current consumption if the vehicle is left for a number of weeks. The system then can only be disarmed using your PIN number , this gives protection even if your keys are stolen, whilst you are away on holiday.
*
Toggles between loud and soft arming/disarming bleeps if selected ( See above note in 7)