Hi @Angelina98
I don't think you do need to announce you have a security system.
However, given how touchy airbnb CS are regarding undisclosed monitors and survellaince and how willing they are to give customers a full refund after staying and close down your listing for a couple of weeks while they "investigate" I would be inclined to hedge my bets.
If it were me, I'd go to Booking Settings - House Rules - Edit - and under surveillance I would type something to the effect that you have a security system only with NO survelliance cameras. This is better than just saying so in your description - this is the bit airbnb check if there is a complaint.
This way you should be better covered.
Other hosts may have other opinons.
Regards