46 CFR § 169.831
Emergency position indicating radio beacon (EPIRB)
April 15, 2021
The master shall ensure that—
(a) The EPIRB required in §169.555 of this subchapter is tested monthly, using the integrated test circuit and output indicator, to determine that it is operative; and
(b) The EPIRB's battery is replaced after the EPIRB is used and before the marked expiration date.