Tait International Limited TPDHBB User Manual

 

Project 25. The Association of Public 
Safety Communications Officials 
(APCO) established Project 25 (P25). 
This project was led by United States 
Federal, state, and local government 
representatives to develop standards 
for interoperable digital radios and 
systems to meet the needs of public 
safety users. 

 

 for further 

information.

P25 Phase 1 refers to radio systems 
operating in 12.5 kHz analog, digital or 
mixed mode on conventional networks 
or in digital for trunking networks. 
Phase 1 digital transmissions are FDMA 
(Frequency Division Multiple Access) 
based and use Continuous 4 level 
Frequency Modulation (C4FM) or LSM, 
a linear modulation for simulcast 
systems.

P25 Phase 2 refers to the P25 digital 
Common Air Interface (CAI), Time 
Division Multiple Access (TDMA) based, 
which provides one voice channel per 
6.25 kHz channel spectrum efficiency. 
The current standards effort focuses on 
2-slot TDMA which provides two voice 
traffic channels in a 12.5 kHz allocation.