In this mode two or more mo- bile staons communicate to each other di- rectly, without the co-ordinaon by a base staon. The commu- nicaon between two mobile staons (MS) always run through the base staon (BS). In this mode, the terminals connect to a base staon (a ﬁxed infrastruc- ture) and are controlled by this. The TETRAPOL system works in mainly three diﬀer- ent modes: Network mode. The Publicly Available Standard (PAS), which de- ﬁnes the various interfaces in a TETRAPOL infra- structure, can be downloaded by registered users. TETRAPOL Forum (provides a collecon of manufacturers of TETRAPOL products. Currently, TETRAPOL is proven around the world with 85 networks in around 30 countries. However, TETRAPOL provides a secure and robust voice and data communicaon in crical situaons.

Diﬀerent to the mobile cell phone, the number of parcipants of a digital trunked communicaon system (as TETRAPOL) is limited. The main users of the trunked communicaon system are closed user groups, such as transport services (taxi, state railway and local transport companies), airports, energy companies and public security agencies (as police, ﬁre brigade, rescue forces, ar- my, civil protecon and boarder control etc.). Today the TETRAPOL technology is supported and further de- veloped by two organizaons: by TETRAPOL- Forum (mainly manufacturer) and User’s club. The ﬁrst users of TETRAPOL were the Gendarmerie (mid 1992) and then the police (early 1995) in France. TETRAPOL was developed by Matra Communica- on (today AIRBUS), France. TETRAPOL oﬀers voice and data services for the most demanding users and professional organizaons for mission-crical communicaons.

TETRAPOL Overview TETRA Operang Mode TETRAPOL is a digital trunked mobile radio stand- ard, using an open, digital, purpose-built PMR (professional mobile radio) technology for mission- crical public safety users.

Radio tetrapol tph700