Project 25 Phases
Both formats are 4800 symbols per second - where each symbol encodes two bits of data for a raw bit rate of 9600 bps.
Project 25 Phase I FDMA
Phase I FDMA consists of a C4FM modulated signal that fits in a 12.5 kHz wide channel or a CQPSK modulated signal that fits in a 6.25 kHz channel. Motorola has established an additional de-facto standard for simulcast with a Phase I compatible variation called LSM. LSM is a CQPSK modulated 12.5 kHz wide signal.
Prior to the final Phase II standard being approved, Motorola developed and implemented their own TDMA protocol known as "X2-TDMA". X2-TDMA was implemented on the following systems:
Prince George's County MD Project 25 System
Loudoun County VA Project 25 System
Apopka County FL Project 25 System
Project 25 Phase II TDMA
The Phase II standard is a 2-slot TDMA signal that fits inside a 12.5 kHz wide channel. This allows existing 12.5 kHz wide license holders to double call capacity by upgrading their infrastructure to Phase II. The Phase II standard was approved in November 2010 , and as of August 2011 Motorola has begun shipping Phase II systems  .
These systems can operate in a mixed-mode configuration of Phase I FDMA and Phase II TDMA. If a Phase I only capable radio affiliates with a Phase II talkgroup, these systems are configured to automatically use Phase I modulation on the frequency.
Scanner Support for Motorola X2-TDMA and P25 Phase II TDMA
Motorola's X2-TDMA protocol can be decoded with the GRE PSR-800 EZ-Scan Digital Scanner. The PSR-800 is currently the only scanner model with the hardware to support any form of TDMA decoding (as of August 14th 2011).
On August 13th 2011, GRE stated that the PSR-800's support for P25 Phase II TDMA cannot be confirmed until it is tested live on a system that uses the final Phase II TDMA standard.
On December 18, 2011, a PSR-800 user confirmed that the PSR-800 cannot currently decode P25 Phase II TDMA (only X2-TDMA).
Uniden has confirmed that none of their current models support TDMA in any form, nor do they have the requisite hardware to do so, therefore cannot be made TDMA compatible via a firmware update. 
X2-TDMA can also be monitored with DSD.
Printed from: Project 25 - The RadioReference Wiki