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The Underwriters Laboratories' UL 294 is a safety standard that addresses the construction, performance, and operation of access control systems intended to regulate or control entry into and exit from secured areas. These systems can also restrict access to certain devices through electrical, electronic, or mechanical means.
Coded panels were the earliest type of central fire alarm control, and were made during the 1800s to the 1970s. A coded panel is similar in many ways to a modern conventional panel (described below), except each zone was connected to its own code wheel, which, depending on the way the panel was set up, would either do sets of four rounds of code until the initiating pull station was reset ...
Control panels and power supply EN 54-2 Part 2: Control and indicating equipment (Fire alarm control panel) 1997 + A1:2006 + AC:1999 Yes Alarm devices EN 54-3 Part 3: Fire alarm devices - Sounders 2014 + A1:2019 Yes Control panels and power supply EN 54-4 Part 4: Power supply equipment 1997 + A1:2002 + A2:2006 + AC:1999 Yes Detectors EN 54-5
Below is a list of NEMA enclosure types; these types are further defined in NEMA 250- Enclosures for Electrical Equipment. Each type specifies characteristics of an enclosure, but not, for example, a specific enclosure size.
UL headquarters in Northbrook, Illinois. Underwriters Laboratories Inc. was founded in 1894 by William Henry Merrill.After graduating from the Massachusetts Institute of Technology (MIT) with a degree in electrical engineering in 1889, Merrill went to work as an electrical inspector for the Boston Board of Fire Underwriters. [9]
The control action is the switching on/off of the boiler, but the controlled variable should be the building temperature, but is not because this is open-loop control of the boiler, which does not give closed-loop control of the temperature. In closed loop control, the control action from the controller is dependent on the process output.
The control protocol is a variation of LIN which retains the analog voltage level signaling from SAE J1772. The positive level of the LIN signal waveform can change from 12 volts to 9 or 6 volts (known as State A, State B, and State C in J1772). An earlier version of this LIN-based control protocol was published in Annex D of IEC 61851 edition 3.
The current rating of smaller NEMA contactors or their auxiliaries are defined by NEMA ICS 5: Industrial Control and Systems, Control Circuit and Pilot Devices [1] standard. The nomenclature is a letter followed by a three-digit number, the letter designates the current rating of the contacts and the current type (i.e., AC or DC) and the number ...