Explanation
A ringer equivalency number of 1 represents the loading effect of a single "traditional" telephone ringing circuit, such as that within the Western Electric Model 500 telephone. Note that the REN of modern telephone equipment may be significantly lower than 1: as a rough guide, externally-powered digital-ring phones may have a REN as low as 0.1, while modern analog-ring phones (where the ringer is powered from the phone line) typically have a REN around 0.8.
In the United States 1 REN was formerly equivalent to a 6930Ω resistor in series with an 8 µF (microfarad) capacitor. The modern ANSI/TIA-968-B specification (August 2009) defines 1 REN as an impedance of 7000Ω at 20Hz (type A), or 8000Ω from 15Hz to 68Hz (type B).
Read more about this topic: Ringer Equivalence Number
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