When I bought my car, I knew that it had an aftermarket alarm system that had been disabled, and in the engine bay some unknown wires are hanging loose (give no problem). I'm now thinking of reactivating/reconnecting the system, so I need to determine what model it is. I'm guess there must be some unit hidden somewhere. System controls the door locks, and turnsignals aswell.
How can I identify what system is in?
In the engine bay there's a black box to turn the alarm on/off with a key, and it's got this code printed: HP15CA-12Vdc

Any help is much appreciated!

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2011 Prius