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Electrical codes require such exposed high voltage equipment to be fenced off from the public, so the mast and antenna tuning hut are surrounded by a locked fence. Usually a chain-link fence is used, but sometimes wooden fences are used to prevent currents induced in a metallic fence from distorting the radiation pattern of the antenna. An ...
In March 2016, Amazon unveiled the original Amazon Echo Dot, [51] which is a hockey puck-sized version of the Echo designed to be connected to external speakers due to the smaller size of the onboard speakers, or to be used in rooms such as the bedroom as an alternative to the full-sized Echo. Despite its smaller form factor, the Amazon Echo ...
Hand telephone sets consist of three principal parts: the handset, a handset mounting, and an apparatus box, called variously desk set box, bell box, subscriber set, or just subset. This box is typically mounted on a wall or desk-side, and contains an electromagnetic bell ringer and a speech transformer , called induction coil , to connect the ...
Amazon Echo Show is a smart speaker with a screen that is part of the Amazon Echo line of products. Similarly to other devices in the family, it is designed around Amazon's virtual assistant Alexa, but additionally features a touchscreen display that can be used to display visual information to accompany its responses, as well as play video and conduct video calls with other Echo Show users.
As a crystal radio has no power supply, the sound power produced by the earphone comes solely from the transmitter of the radio station being received, via the radio waves captured by the antenna. [3] The power available to a receiving antenna decreases with the square of its distance from the radio transmitter. [46]
The device, a passive cavity resonator, became active only when a radio signal of the correct frequency was sent to the device from an external transmitter. This is referred to in NSA parlance as "illuminating" a passive device. Sound waves (from voices inside the ambassador's office) passed through the thin wood case, striking the membrane and ...
The AN/PRC-77 entered service in 1968 during the Vietnam War as an upgrade to the earlier AN/PRC-25.It differs from its predecessor mainly in that the PRC-77's final power amplifier stage is made with a transistor, eliminating the only vacuum tube in the PRC-25, as well as the DC-DC voltage converter used to create the high plate voltage for the tube from the 15 V battery.
The purpose of perimeter fence is to stop or prevent the incident and reduce the level of risk. Doing so discourages the perpetrator from completing a harmful event. For example, a high wall with fence posts that protects a property discourages criminals from intruding and, when an incident occurs, increases the time it takes to carry it out.