The purpose of CTCSS is to reduce co-channel interference during band openings. CTCSS repeaters would respond only to signals having the CTCSS tone required for that repeater. These repeaters would not respond to distant weak signals on their inputs and would not repeat those signals.

Listed are the standard Electronic Industries Association (EIA) 
frequency codes, in hertz, along with their Motorola alphanumeric designators. 

 67.0 - XZ          97.4 -  ZB            141.3 - 4A            206.5 -  8Z
 69.3 - WZ          100.0 - 1Z            146.2 - 4B            210.7 -  M2
 71.9 - XA          103.5 - 1A            151.4 - 5Z            218.1 -  M3
 74.4 - WA          107.2 - 1B            156.7 - 5A            225.7 -  M4
 77.0 - XB          110.9 - 2Z            162.2 - 5B            229.1 -  9Z
 79.7 - WB          114.8 - 2A            167.9 - 6Z            233.6 -  M5
 82.5 - YZ          118.8 - 2B            173.8 - 6A            241.8 -  M6
 85.4 - YA          123.0 - 3Z            179.9 - 6B            250.3 -  M7 
 88.5 - YB          127.3 - 3A            186.2 - 7Z            254.1 -  0Z
 91.5 - ZZ          131.8 - 3B            192.8 - 7A 
 94.8 - ZA          136.5 - 4Z            203.5 - M1

CTCSS TONE FREQUENCIES