The IC-M604 has excellent receive specifications which allow a weak signal a better chance of being heard when louder signals are around it. The powerful 5.0W (typical) audio output from the front facing speaker further increases the audibility and quality of received calls. The large full dot-matrix display is designed for optimum readability in any lighting condition. With the extra large font, the channel number is maximized on the display and upper and lower case characters can be easily read. When connected to an external hailer horn, communication with other boats, deck or dock hands is easy. The built-in 30W amplifier increases your talk power making your message loud and clear. Four foghorn patterns are also available. The IC-M604, including the supplied microphone, withstands submersion in up to 1.0m depth of water for 30 minutes. It is equivalent to IPX7 waterproofing. No matter what channel you are tuned to, a separate and independent receiver inside the M604 continuously monitors Ch. 70. The 10-keypad allows simple and efficient operation of the DSC emergency functions, vital for your safety at sea. Over and above the DSC, your own and other ships position data can be exchanged with the position request or position report functions. The received position information can be transferred to external GPS or navigation equipment. In addition, the polling (request/ reply) function checks whether a specific ship is within the communications range. When connecting to an external GPS receiver, the GPS information indication function shows course and speed data as well as position, date and time on the display. The speaker microphone can be detached from the front panel and can be connected to the rear panel without any modification. An optional 6.1m (20ft) microphone extension cable, OPC-1000, is available. The RX speaker function, receiver-repeater allows you to monitor the received radio audio from a hailer horn on the deck or tower. You can also make an announcement on-board from the microphone. This function allows quicker channel selection. Set the TAG channel to the channels used most often. When pushing the up/down buttons on the speaker microphone, only tagged channels are selected and untagged channels are skipped. The TAG scanning function detects only tagged channels. Dual/tri-watch function for monitoring Ch.16 and/or call channel. 7 levels adjustable backlit display and keypad. Optional voice scrambler, UT-112 for private communication. Weather channels with weather alert function. AquaQuake draining function emits a vibrating sound and clears water away from the speaker grill.