46 CFR §113.35-5

1. (a)Each electric engine order telegraph system must have transmitters and indicators that are electrically connected to each other.
2. (b)Each engineroom indicator must be capable of acknowledgment of orders.
3. (c)There must be an audible signal at each instrument. The signal at both locations must sound continuously when the transmitter and the indicator do not show the same order.
4. (d)Each telegraph instrument must meet the protection requirements of § 111.01-9 of this chapter.
5. (e)Each system must have an alarm which—
   1. (1)Automatically sounds and visually signals a loss of power to the system;
   2. (2)Is on the navigating bridge; and
   3. (3)Has a means to reduce the audible signal from 100 percent to not less than 50 percent.