MM-015371-001
The radio must be powered by an external +13.6-volt (nominal) DC power source. In motorcycle
applications, the motorcycle’s electrical system is utilized as the source of DC power. The control head
connected to the radio is also powered by the same DC power source, but separately fused. When the
control head is powered-up by the operator, it “wakes up” the radio by transmitting data to the radio via
the CAN link.
The radio provides half-duplex voice and data communications. Voice communications are accomplished
via a “push-to-talk” (PTT) type microphone and a speaker connected to the control head.
For data communications, the radio has an industry-standard 9-pin serial interface port for connecting
optional data-type equipment, such as a Mobile Data Terminal (MDT), a laptop PC, an external display,
or a key-entry device. This port works seamlessly with equipment from popular manufacturers and off-
the-shelf applications. OpenSky employs User Datagram Protocol over Internet Protocol (UDP/IP) data
packet transfers, providing “plug and play” connectivity for data-type devices.
800 MHz operating bands of the radio include 806 to 824 MHz repeater input band (mobile transmit) and
the 851 to 869 MHz band used for repeater output and talk-around communications.
The radio has an optional built-in Global Positioning System (GPS) tracking receiver. GPS provides
quick and accurate unit location information to dispatchers via the radio network. The GPS receiver
determines the unit’s location and the radio transmits it to the radio network. The GPS antenna is
mounted completely separate from the mobile transmit/receive antenna.
The radio and control head exceed tough environmental specifications included within military standard
MIL-STD-810F, the radio industry standard TIA/EIA-603, and the radio standard established by the U.S.
Forest Service.
An M7300 mobile radio operating on an OpenSky radio network uses Time-Division Multiple-Access
(TDMA) digital modulation technology on the radio frequency link. TDMA allows multiple radio users to
share a single RF channel. In addition, a single RF channel can support simultaneous digital voice and
data communications.
OpenSky employs Advanced Multi-Band Excitation Plus (AMBE+) speech and data compression
technology developed by Digital Voice Systems, Inc. When operating on an OpenSky radio network,
AMBE+ gives an M7300 radio the ability to provide exceptional voice quality via the limited bandwidth
of the radio frequency path, even when the received RF signal is weak (i.e., even in “fringe” areas).
AMBE+ is performed by a Digital Signal Processor (DSP) integrated circuit within the radio programmed
to perform an AMBE+ compression algorithm during mobile transmissions, and an AMBE+ expansion
algorithm during mobile reception.
Speech compression electronic circuitry—be it AMBE+ or another type such as IMBE—is sometimes
referred to as “vocoding” circuitry for voice coding, or simply a “vocoder” circuit.
The M7300 mobile radio also supports radio operation on 800 MHz APCO Project 25 Phase I compliant
Common Air Interface (P25 CAI) trunked radio networks, and operation in a talk-around mode in
accordance with the APCO Project 25 Phase I standard. P25 radio systems utilize Improved Multi-Band
Excitation (IMBE) speech/data compression technology, also developed by Digital Voice Systems, Inc.
Like AMBE+ technology, IMBE technology gives the M7300 mobile radio the ability to deliver
exceptional voice quality, even in areas where the received RF signal strength is weak. IMBE replicates
human speech better than other voice compression technologies, resulting in better voice quality and
better speaker recognition. The Telecommunications Industry Association (TIA) funded an independent
study to evaluate compression technologies. The findings showed that when compared with other
industry-recognized compression technologies, IMBE provided the highest voice quality. In the study,
radio users were asked to listen to coded speech produced by four different compression technologies
(i.e., vocoder circuits) operating under a variety of conditions. The users rated the speech on a scale of
one to five, with five being the best quality. Under each operating condition, IMBE was rated the best.
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