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Producers are looking to new truck-tracking systems that generate more signals to maintain continuous contact between dispatcher and driver. The systems generate so many signals that many private license-holders find their allotted frequencies full. Producers can solve the problem by subscribing to provider-specific wireless technologies including cellular digital packet data (CDPD), enhanced specialty mobile radio (ESMR) or Linear Modulation. CDPD technology allows producers to send signals through networks of antennas and transmission stations installed for cellular phone service. Signal heads in trucks encode signaling data into digital transmission bursts (packets) based on Industry Standard Internet Protocol. The data heads transmit these packets to cellular system antennas during intervals in other subscribers' voice transmissions. ESMR enables users to send both voice and data over the same radio. Microphones are equipped with special encoders that transform voice transmissions into digital signals rather than analog signals. Linear Modulation technology channels signals at 5-kilohertz intervals, increasing the capacity of the signals' frequency and allowing full utilization of truck-tracking systems.