FAR/AIM: § 121.582 Means to discreetly notify a flightcrew.

Except for all-cargo operations as defined in § 110.2 of this chapter, after October 15, 2007, for all passenger carrying airplanes that require a lockable flightdeck door in accordance with § 121.313(f), the certificate holder must have an approved means by which the cabin crew can discreetly notify the flightcrew in the event of suspicious activity or security breaches in the cabin.