From The RadioReference Wiki
Tetrapol is an trunking standard developed by EADS Telecom (Formerly MATRA) and is in use primarally in police and military in Europe.
Tetrapol is based on an FDMA (frequency division multiple access) multiplex approach using a narrow-band channel operating at 12.5 KHz. Tetrapol uses GMSK modulation instead of the pi/4-QDPSK used by TETRA
Since 1988, when TETRAPOL was chosen for the world's first implementation of a large-scale digital PMR network (RUBIS for the French National Gendarmerie), its subsequent success has been unstoppable accross europe and worldwide, being adopted by a wide range of civilian, military, public safety, and other security organisations.
There are today 60 TETRAPOL networks deployed or in the process of being deployed in 28 countries.
Tetrapol uses by default strong end to end crypto.
There is not a scanner available today that can monitor Tetrapol.