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The Number Five Crossbar Switching System (5XB switch) is a telephone switch for telephone exchanges designed by Bell Labs and manufactured by Western Electric starting in 1947. It was used in the Bell System principally as a Class 5 telephone switch in the public switched telephone network (PSTN) until the early 1990s, when it was replaced ...
A Class-5 switch provides telephone service to end customers locally in the exchange area, and thus it is concerned with "subscriber type" activities: generation of dial-tone and other "comfort noises"; handling of network services such as advice of duration and charge etc. Specifically, a class-5 switch provides dial tone, local switching and ...
In building wiring, multiway switching is the interconnection of two or more electrical switches to control an electrical load from more than one location.A common application is in lighting, where it allows the control of lamps from multiple locations, for example in a hallway, stairwell, or large room.
The units of specific contact resistivity are typically therefore in ohm-square metre, or Ω⋅m 2. When the current is a linear function of the voltage, the device is said to have ohmic contacts. Inductive and capacitive methods could be used in principle to measure an intrinsic impedance without the complication of contact resistance.
The Lucent 5ESS, a class-5 switching system, is sometimes used as a class-4 switch (or as a mixed class-4/5 switch) in markets that are too small to justify a 4ESS switch. The Nortel DMS-250 , a larger variant of the DMS-100 , is a popular competitor to Lucent's 4ESS, especially among telephone companies that were not previously a part of AT&T.
Switching uses different kinds of network switches. A standard switch is known as a layer-2 switch and is commonly found in nearly any LAN. Layer-3 or layer-4 switches require advanced technology (see managed switch) and are more expensive and thus are usually only found in larger LANs or in special network environments.
[2] [3] Shunts are rated by maximum current and voltage drop at that current. For example, a 500 A, 75 mV shunt would have a resistance of 150 microohm, a maximum allowable current of 500 amps and at that current the voltage drop would be 75 millivolts. By convention, most shunts are designed to drop 50 mV, 75 mV or 100 mV when operating at ...
The switch will operate in a make-before-break mode provided both sources are acceptable and synchronized. Typical parameters determining synchronization are: voltage difference less than 5%, frequency difference less than 0.2 Hz, and maximum phase angle between the sources of 5 degrees.