Only the DN's will do the 2.5 Khz steps necessary to program in one of the newer splinter channels, ie. 153.777500. The AN-CN models will do the new 12.5 Khz channel spacing spec, but only for non-splinter frequencies like 155.235000.
In many cases, earlier models will still be very serviceable for many years to come. But when an agency licenses and implements a splinter channel some time in the future, the earlier models won't be programmable to the new frequencies.
Rochester-Monroe County 911 7010 1976 to 2003
Northampton Ambulance - Car 2829
KD2IAT --- WQPG808