HT 1250s all have 128 channels. I have NO idea what you mean by "pre and Post tx".
Fromm Motorola .com:
Highlights of the Motorola HT1250™ Portable Two Way Radio
Battery Life (based on 5/5/90 duty cycle) - 8 hours
Call Tones - Quik Call II™
Channels - 128
Cloning - With Cable
Coverage - Programming Software allows adjustable power output for varying coverage
Dimensions H x W x L (with standard battery) - 5.4" x 2.26" x 1.5"
Display - Yes
Emergency Button - Yes
Frequency - Low Band (29.7-42, 35-50MHz), VHF (136-174MHz), UHF (403-470, 450-512MHz)
Front Panel Programmable - No
Interference Eliminator Codes - 42 PL, 84 DPL
Intrinsically Safe - Option
Keypad - Yes
Mil Spec - 810 C, D, E
Model Includes - NiMH Battery, Intelli-Charger, Belt Clip, Antenna, Operating Instruction Manual
Option Board Available - Yes
Power - 4W-UHF, 5W-VHF, 6W-Low Band
Programmable Buttons - 7
Signaling - Quik Call II™, DTMF, MDC-1200
Technology - Analog
VibraCall - No
Voice Activation (VOX) - Yes
Warranty - Two Year Warranty
Weight (with standard battery) - 15 oz.