The electrical energy necessary to power a sound-powered telephone's small vibrating bell is obtained from what power source?

Correct Answer: Option D — each station's hand-cranked generator

Sound-powered telephones operate entirely independently of the ship's external power grid. Complying with 46 CFR Subchapter J emergency communication requirements, each individual station utilizes an integral hand-cranked magneto generator to supply the electrical energy required to ring the remote station's vibrating call bell.