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Rumbler siren. A Rumbler siren is a type of emergency vehicle siren used primarily in the United States.Developed in 2007 by Federal Signal Corporation, and sounding at a low-frequency level, it is designed to be heard by motorists who may otherwise be unable to hear high-frequency sirens due to ambient noise, such as urban traffic.
A beam compass and a regular compass Using a compass A compass with an extension accessory for larger circles A bow compass capable of drawing the smallest possible circles. A compass, also commonly known as a pair of compasses, is a technical drawing instrument that can be used for inscribing circles or arcs.
The Modulator has a similar setup to the Whelen WPS 2700, 2800, 2900, and OmniAlert omnidirectional speaker arrays. The Whelen arrays have single driver cells, [3] while Modulators have multi-driver cells. The American Signal I-Force siren, which uses stacked, elliptical speaker cells that provide omnidirectional sound output, is also similar ...
A beam compass is a compass with a beam and sliding sockets or cursors for drawing and dividing circles larger than those made by a regular pair of compasses. [1] The instrument can be as a whole, or made on the spot with individual sockets (called trammel points) and any suitable beam.
Some central office switches in the United States, notably older GTD-5 EAX systems, utilize a single frequency tone, 480 Hz, known as High Tone for this purpose. In either case, the tone is substantially louder than any other signal transmitted over a copper POTS circuit; loud enough to be heard across a room from an unused off-hook telephone.
The .400 Whelen cartridge was developed by Colonel Townsend Whelen while he was commanding officer of Frankford Arsenal in the early 1920s. [2] The cartridge resembles a .30-06 Springfield case necked up to .40 caliber to accept bullets manufactured for the .405 Winchester .
Late 19th-century reduction compass. The reduction compass or proportional dividers is a geometry tool with asymmetric-length branches to allow performing homothetic transformations, reproducing a pattern while enlarging or reducing its size and conserving angles. It was invented by Fabrizio Mordente before 1567.
A circumferentor, or surveyor's compass, is an instrument used in surveying to measure horizontal angles. It was superseded by the theodolite in the early 19th century. [1] A circumferentor consists of a circular brass box containing a magnetic needle, which moves freely over a brass circle, or compass divided into 360 degrees.