Understanding Ring Generators

A Ring Generator (RG) is an electronic power device used in the telecom industry to generate the ringing signal for telephones. It is a DC/AC inverter that accepts a usual DC input voltage of 48V and produces an output AC voltage from 120 to 300V peak-to-peak. The output frequency range is from 17Hz to 70Hz. Most high-quality generators have an isolated output and their peak-to-peak voltage is centered around 0V, in other words, the output voltage swings as much negative as it does positive with respect to ground. It is designed to have the same characteristic as any household AC outlet, the only difference is the AC outlet provides 110 to 220VAC at 60Hz or 50Hz. The ring generator typically provides 45 to 90VAC at different frequencies. The low frequency is needed for electromechanical bell telephones. Old telephone sets equipped with these mechanical bells use a large inductor (electromagnet) to drive the hammer, as is shown in Figure 1.