TeleType GPS .ttm files are based on U.S. County maps. The TeleType GPS program provides a simple way to load maps, simply click on the city or town for which you want to load street maps. For those who need a correlation between .ttm files and county names you can use the following link provided by the U.S. Environmental Protection Agency (EPA) to determine state and county codes.

http://www.epa.gov/enviro/html/codes/state.html 

or another link provided by the U.S. Census Bureau (which also includes latitude and longitude coordinates

http://www.census.gov/ftp/pub/tiger/tms/gazetteer/counties.txt

The TeleType GPS .ttm map files are composed of five digits. The first two are the state code, the last 3 are the county code.

Example: Middlesex county in Massachusetts is: 25017  (25 = Massachusetts, 017 = Middlesex county)

Using the TeleType GPS CD-ROM locate the folder called 25_MA (inside the Maps folder), then select both of the corresponding tgr files, in this case it would be:

tgr25017p2.ttm    and    tgr25017nr.ttm