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Security Dealer & Integrator
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Interrogate The Integration Expert
Protocols Involved with NetworksThe Latest from SIW
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By Tim O'Leary
Q: Can you define some of the protocols involved with networks used in security and integration?
A: Here is an overview of some protocol flavors you'll encounter in system integration. Something to watch out for is having to adapt products to applications for which the native protocol of a device is not suitable for the situation. An example of this is connecting Wiegand readers over long distances (check out “An Open & Shut Case” in the October 2006 Security Dealer ).
Cat 3 : Used for data networks using frequencies up to 16 MHz, mainly for telephone cables.
Cat 5e : Up to 125MHz. Used for 100Mbit/s and gigabit Ethernet networks.
Cat 6 : The cable standard for Gigabit Ethernet that is backward compatible with the Category 5/5e and Category 3 cable standards. Suitable for 10BaseT/100BaseTX and 1000BaseT (Gigabit Ethernet) connections. It provides performance of up to 250 MHz.
RS-232: Standard for serial binary data interconnection commonly used in computer serial ports. The maximum cable length is 50 feet, or the cable length equal to a capacitance of 2500 pF . Using a cable with low capacitance allows you to span longer distances. If UTP CAT-5 cable is used with a typical capacitance of 17 pF/ft , the maximum allowed cable length is 147 feet. RS232 standard was originally developed for 20 kbps . By halving the maximum communication speed, the allowed cable length increases by a factor of ten!
EIA-422: (formerly RS-422 ), now TIA-422 , is a technical standard which provides for data transmission, using balanced or differential signaling, with unidirectional/non-reversible, terminated or non-terminated transmission lines, point to point, or multi-drop. In contrast to RS-485 (which is multi-point), EIA-422 allows one driver and multiple receivers. Maximum data rates are 10 Mbit/s at 1.2 m or 100 kbit/s at 1200 m. EIA-422 cannot implement a truly multi-point communications network (such as with EIA-485), but one driver can connect to up to ten receivers.
