Transportation Security Administration

The Transportation Security Administration, or TSA, is a part of the the Department of Homeland Security.

The following is the channel plan from the radios and the descriptions from list on the front of the radios. As you can see some of the channels have the same frequencies (i.e. 1 thru 4). These channels use digital "Network Access Codes" (or NAC's) which are similar in funciton to PL or DPL tones. They allow the channels to function independently from each other while still using the same frequency; the exception to this is Channel 10 which can be heard on Channel 7.

National Radio Channel Plan
 
 Ch 1  172.1500 NAC 001  S1 Simplex 1
 Ch 2  172.1500 NAC 002  S1 Simplex 2
 Ch 3  172.1500 NAC 003  S1 Simplex 3
 Ch 4  172.1500 NAC 004  S1 Simplex 4
 Ch 5  172.9000 NAC 002  S2 Simplex 2
 Ch 6  169.3000 NAC 009  S3 Simplex 
 Ch 7  172.9000 NAC 001  R1 Repeater 1
 Ch 8  172.9000 NAC 002  R1 Repeater 2
 Ch 9  172.9000 NAC 003  R1 Repeater 3
 Ch 10 172.9000 NAC 001  S2 Simplex 1
 Ch 11 172.9000 NAC 003  S2 Simplex 3
 Ch 12 166.4625 PL 103.5 F1 Simplex 1 (Analog, DHS Common)
 Ch 13 166.4625 NAC 001  F1 Simplex 2 (Digital, DHS Common)
 
 *Note: Channel 6 (169.300) is used as the input to the R1 (172.900) repeaters
  in channels 7, 8, and 9. The use of different NAC's allows traffic on
  Channel 6 to remain seperate and function as a simplex channel without
  activating the repeater.

Other Frequencies
 169.1625 NAC 128  Dallas/Fort Worth Int'l
 169.1875 Unk      Dallas/Fort Worth Int'l
 172.9000 NAC 128  Dallas Love Field (Ch 5)
 169.1625 Unk      Chicago O'Hare
 469.5000 DPL 023  San Fransisco Int'l (TSA Contractors)