Using the RS-MS1A with older Icom radios
See information on this page: http://iz2lxi.jimdo.com/english/using-app-rsms1a-with-older-radios-like-ic-2820/
Icom ID-51A Plus CI-V Settings for RS-MS1A
Menu> Function> CI-V and make all the setting show like this.
CI-V (DATA Jack) ON (Echo Back Off)
CI-V Address 86
CI-V Baud Rate 9600 bps
CI-V Transceive On