No. The more users tracked by GPS, the more carrier frequencies, and each carrier frequency can support 2048 users at most.

　　There is no specific requirement. MMS supports the current mainstream picture format, but you are proposed to choose pictures of a medium resolution of approximately 160X128. If pictures are of too high resolution, the effect of receiving pictures will be affected.

　　PDT digital trunking system can interconnect with MPT analog trunking system through wired or wireless gateway access and implement the function as groups of calls. Furthermore, PDT digital trunking system can operate simultaneously in PDT mode and MPT mode and the terminals supporting the two modes can access the network and operate at the same time, which can facilitate the smooth transition for users.

　　PDT digital walkie-talkie can not only achieve satellite positioning but also support Beidou positioning function to facilitate logical choice by users.

　　At present, the industrial users in our country use the above 3 trunking systems. PDT digital trunking system has absorbed the advantages of Tetra and MPT, so its coverage area is the same as that of MPT, but 9 times that of Tetra.

　　On March 20, 2013, the Ministry of Public Security officially issued 4 industrial technical standards including Overall Technical Specifications for the GA/T1056-2013 Police Digital Trunking (PDT) Communication System, etc. The launch of the PDT police digital trunking equipment standards and related products will effectively promote the development and construction of wireless communication digitalization for public security, civil air defense, etc., and at the same time will break the monopoly of digital trunking by foreign manufacturers and introduce competition into the industry so as to improve the product performance and reduce the cost. This standard with independent intellectual property rights will also benefit the other domestic professional departments in the development of wireless digital communication and promote the development of national industry. Because of the important status of our country and the size of the digital trunking, PDT is expected to become one of the three international digital trunking communication standards.

　　At present, under the guidance of the professional digital trunking (PDT) industry technology innovation strategic alliance, the PDT industry from the development of chips to the equipment integration has formed a complete industrial chain, and many domestic manufacturers has completed the R&D of the PDT switching equipment, base station, terminal, encryption, network management and has brought them into the stage of commercial use. Until the end of September, 2013, each manufacturer had completed and signed 45 construction contracts for the PDT system. The public security departments at all levels in about 15 provinces, municipalities and autonomous regions across the country have begun the planning and construction of public security 350 million PDT trunking system, and have built more than 30 exchange centers, more than one hundred PDT base stations, and equipped with tens of thousands of PDT terminals. And these equipment has been applied in communication projects of the countries such as Russia, Thailand, Pakistan and Nepal, etc.

　　Both AP-330 handsets and AP-550 vehicular-locating set can provide 4 operating modes such as PDT trunking, analog trunking, PDT conventional and analog conventional, which can support conventional intercom and analog network access to realize the smooth transition of user's system from analog to digital.

　　The integrated dispatch stations of ID series conduct wireless communication by providing exchange control platform and control interface, equal to access to gateway and to a variety of wireless (including conventional signal transmission, trunking, public network) user terminals or to the built-in module and also by providing all kinds of cable interface (outside and inside, Ethernet, satellite phones) to access subscriber line communications cable so as to realize the integration of all kinds of standard communication systems to facilitate the unified dispatch and command of various dispatch and command centers and emergency communication vehicles.

　　TETRA standard is the open digital trunking standard formulated by the European Telecommunication Standards Institution (ETSI).

　　Its advantages mainly include:

　　. High data transmission rate;

　　. Support of higher user density;

　　. Earlier promotion, and maturation and stability of the product, used in more than 80 countries and regions all over the world;

　　Its disadvantages mainly include:

　　. Cellular system, higher cost of network creation and maintenance;

　　. High-class encryption protocol not open to countries outside Europe:

　　. No confirmed and unified standards for system interconnection and interworking, systems of different manufacturers can be interconnected within;

　　. Monopoly of foreign manufacturers and low localization.

　　PDT standard is the professional wireless communication digital trunking standard with .China’s independent intellectual property rights.

　　Its advantages mainly include:

　　. Regional system, lower cost of network creation and maintenance;

　　. Independent encryption algorithm, and higher security;

　　. Compatibility with analog, in support of achieving the smooth transition of analog system to digital system and protecting existing investments;

　　. A variety of functional application by police;

　　Its advantages mainly include:

　　. In the market introduction period, there is a mature period awaiting the standard and product;

　　. Lower data transmission rate.