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Serial servers are used to connect serial devices to networks, such as local area networks (LAN) or Ethernet. Serial servers are specifically designed to allow industrial devices to be directly accessible from the network without additional hardware. Because network cables can be used in place of serial cables and connectors, serial servers minimize workstation clutter and allow serial devices to be placed far away from the computer or peripheral device they interface with.
For general information about a serial device's network, serial protocol, connectors, and form factor, please see the Serial Adapter Selection Guide on GlobalSpec. Other important specifications include number of ports, data rate, and agency approval.
Ports and Data Rate
Most serial servers have multiple ports, which allow a user to connect several devices to a single serial port. Buyers may specify the number of serial ports, and should check to ensure that a product contains enough ports to accommodate all devices related to their intended application. By incorporating modular additions with an existing server, the number of available ports may be further expanded, usually by a multiple (ie. expanding 16 ports to 64 ports).
A 48-port serial server. Image credit: Cybernetech
Buyers may also specify data rate, expressed in some form of bits per second (bps). Data rate is closely tied to a serial server's protocol. For example, a server using RS-232 would have a maximum data rate of 20 kbps, while an RS-422 device could theoretically communicate at the much faster speed of 10 Mbps.
Serial servers may be approved by a standards body or agency.
The Federal Communications Commission (FCC) is a U.S. agency that regulates all commercial electronic devices that have clocks or oscillators that operate at frequencies greater than 9 kHz. The FCC therefore oversees most products involving microprocessors as well as radio frequency (RF) devices.
The Restriction of Hazardous Substances directive (RoHS) is a European Union directive which restricts the use of six hazardous materials in the manufacture of electronic and electrical devices. Although they are often simply referred to as "lead-free", RoHS products contain less than 0.1% of lead, mercury, cadmium, hexavalent chromium, polybrominated biphenyls, and polybrominated diphenyl ether.
A Conformité Européenne (CE) mark ensures that a product complies with European Union (EU) legislation and may be placed on the European market. A CE mark is not legally required to certify a product's quality, but often ensures quality in specialty applications such as medical use.
Underwriters Laboratory (UL) is a U.S. product safety certification organization that develops standards and test procedures for products, materials, components, and tools. The Canadian Standards Association (CSA) is a comparable standards organization for products manufactured in Canada. The registered mark of the UL or CSA indicates that a product has been tested and certified to meet the organization's recognized standards.
The Waste Electrical and Electronics Equipment (WEEE) directive is a European Union (EU) order encouraging the recycling or reuse of waste electrical products. The WEEE directive establishes criteria and requirements for the collection, treatment, recycling, and recovering of waste products, and holds the producer responsible for carrying out these actions.
Left to right: a typical RoHS mark | CE mark | WEEE mark
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