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CD Start Page | DATA ACQUISITION ONLINE Page | DATA ACQUISITION PRODUCTS Page |
The LDM85 is a small, inexpensive fiber optic transmitter/receiver. It features a complete RS-232 port as well as high speed TTL/RS-422/ RS-423 data transmit and receive. It is capable of data rates from DC to 5M baud. A pair of these units allows most RS-232C cable links to be replaced and extended with a duplex fiber optic cable. The normal 50-foot RS-232 limit may be extended to 1.2 miles (2 km). Fiber optic data communications provide complete EMI/RFI rejection, isolation, elimination of ground loops, and reduced error rates. Data security is enhanced by almost nonexistent electromagnetic emissions. A unique multipoint capability allows local area networks to be formed with the isolation and data security of a fiber optic data highway.
The LDM85 is packaged in a rugged aluminum enclosure small enough to mount on the back panel of typical computer equipment, saving valuable desk and floor space. The RS-232 connection is through male or female EIA 25-pin connectors. The fiber optic connection is either through SMA (905) or ST connectors. Additional features include a TD/RD reversing switch for connection to DTE (Data Terminal Equipment) or DCE (Data Communication Equipment) ports, three diagnostic LED indicators, and locally connected handshake lines. The TTL port combined with the RS-232 port may be interfaced to RS-422/423 ports.
Recommended Cables
The LDM85 optical transmitter is optimized for launching power into fiber sizes
85/125, 100/140, and 200╡m plastic coated silica (PCS). Due to a lensed optical
system, receiver response does not vary with fiber size.
Multipoint Operation
Local area networks are easily implemented with LDM85. When a talker unit
raises Request To Send (RTS), its data is communicated to all other devices on
a common loop. Data returns to the sending unit, verifying physical integrity
of the loop. Alternately, if pin 16 is strapped to pin 17, echo will be
inhibited. Units may be ordered with this connection made internally. For
multipoint installations, it is important that power be applied to all LDM85s.
For small networks it will likely be acceptable to power each unit from a local
source. Larger networks may benefit from routing a common low voltage power bus
along with the fiber optic cable. An AC bus with isolation transformers at each
unit will preserve system resistance to electrical disturbances. The wide low
voltage AC and DC tolerance makes voltage drop on this bus easily accommodated.
Power
AC or DC power may be applied to the screw terminals or to pin 9 of the 25-pin
connector. Alternatively the unit may be powered by +5 Vdc on pin 18.
VIEW an Adobe Acrobat pdf file for more product info (requires Acrobat Reader).
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