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A ringer box is a telephone signaling device, similar to a bell box. It usually contains an electromechanical gong and was used with most early desk stand telephones, including the candlestick telephones, and the Western Electric type 102 and 202 telephones, which were too small to hold a ringer or other needed electrical components. Many pay station telephones also used a separate ringer box.
In telephony, ringer boxes, and similar devices, are often categorized as subscriber set.
Ringers were commonly placed in the same housing as the subscriber set, which consisted of other electrical components, such as induction coils, capacitors, and, if required, a magneto generator. The subscriber set interfaced a telephone set to the telephone network, while magneto generators were used in a manual exchange to generate a remote ring signal.
The Western Electric 302-type telephone was the first widely used Bell System telephone to include the ringer and other subscriber set components inside the same housing of the telephone set.
A ringer box consists of bells or gongs and an electromagnetically-driven clapper which strikes the gongs when actuated. The electromagnet of the clapper responds to the alternating current sent from a central office exchange or another phone via the telephone network wiring. The direct current required by the telephone's audio circuitry is blocked with a capacitor before entering the ringer to prevent the ringer from being triggered by circuit interruptions and pulse dialing. Typical ring voltages are in the range from 60 to over 100 Volts, and alternate at a frequency of 20-30 Hertz.
Almost all telephones manufactured since the Model 302 telephone was introduced, have an internal phone ringer.
Ringer boxes where produced by all manufacturers of customer-premises telephone equipment. In North America, the prominent producers were Western Electric, Automatic Electric, Kellogg Switchboard & Supply Company, while in Europe companies such as Siemens & Halske and Ericsson mass-produced devices.