SEM910
Introduction
The SEM910 family of products from Cirronet
™
Incorporated provides wireless Ethernet
connectivity between networks located more than 5 miles apart. Built around the WIT910
frequency hopping spread spectrum data modem, SEM products provide a 10/100BaseT
connection to Ethernet networks. SEM products operate in a point-to-point mode or a point-to-
multipoint mode using a star configuration. The center of the “star” is the Master device and the
remote SEMs are Slave devices. Peer-to-peer communication is accomplished by using the
master SEM device to relay datagrams from one slave SEM device to another slave SEM device.
SEMs come in heavy duty, aluminum enclosures suitable for the rugged industrial environment.
The D models come in a DIN rail mount, rugged enclosure designed for factory and industrial
applications. The X models features a remote radio housed in a NEMA 4X/IP66 rated enclosure
that can be mounted outdoors up to 300 feet from the network connection. Communication
between SEM products is performed using the WIT910 over-the-air protocol.
SEM products are 802.3 compatible but not 802.11 compatible, provide 70Kbps full duplex data
throughput and are certified by the FCC.
The SEMs enjoy the same benefits of frequency-hopping spread spectrum technology that the
WIT910s do. Namely, the immunity to multipath fading and resistance to jamming that is
provided by changing frequency every few milliseconds.
The radios in SEM products include a robust over-the-air protocol. This protocol insures error-
free data through the use of a 24-bit CRC and ARQ to detect errors and to automatically request
a retransmission. All of this is transparent to the network which just sees complete error-free
data.
©
2000- 2004 Cirronet
™
Inc
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