Uniden MHS050 Owner's Manual page 17

Operation
When you press (BOOST) when the transmit power is low
(Lo - 1W) the radio transmits at maximum high (Hi - 2.5W)
power (except for channel 75 and 76).
NOTE
4. When you have finished speaking, release the (PTT) or (BOOST) to
listen for a response. TX indicator then disappears on the LCD.
UNIDEN MHS050
17
Handheld VHF Marine Transceiver