ICOM M604 has excellent receive specifications which allows a weak signal a better chance of being heard when louder signals are around it.The ICOM M604 powerful 5.0W (typical) audio output from the from front facing speaker 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, ommunication with other boats 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 availabe Over and above the DSC, your own and other ships' position data can be exchanged with the position request or position report functions,received position information can be transferred to external GPS or navigation equipment. In addition, the polling (request/ reply) function checks wether a specific ship is within the communications range. NMEA 0183 format is required> 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.