I think that's how it works. Unless you have some sort of proprietary
equipment that uses a hinky system.

Doesn't appear to be the case -- For example: Furuno device (navtex) accepts zda
but doesn't even look at RMC...


Here's a link that may help you out.

http://www.gpsinformation.org/dale/nmea.htm#intro

Just puled up a host-search engine thing....