The module can interface directly to a
UART. The range is up to 40 miles using high-gain antennas and outdoor,
line-of-sight transmissions at 9600 bps or less. The transmitter uses
spread-spectrum technology and encryption.
The modules can transmit and receive raw data or implement either of two
built-in methods of error detecting with retries. A command can configure a
module to look for an acknowledgement after transmitting a packet of data. If
the acknowledgement doesn??™t arrive, the module automatically retries the transmission
up to a specified number of times. Another command can configure
the module to repeat all transmitted data a specified number of times.
These modules are just a sampling of what??™s available. The vendors mentioned
above and others offer products to suit just about any application??™s needs.
. !
Several standards define interfaces and protocols for transmitting RF data in
formats other than asynchronous serial data. Modules are available that contain
intelligent controllers that convert between asynchronous serial data and these
interfaces. Table 8-1 compares three options.
9
The Zigbee standard (zigbee.org) defines a hardware interface and software protocols
suitable for monitoring and control functions and other applications that
transmit data in networks at up to 250 kbps. The components are inexpensive
and consume little power.
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