The Model 258, known as the Dual Oscillator, consists of two (2) nearly identical Oscillators. Both can produce frequencies from 5Hz to 20kHz. Oscillator 1 features a continuously variable waveform from sine to sawtooth. Oscillator 2 features a continuously variable waveform from sine to square wave. Both oscillators are meant for audio only, made clear by the presence of tini-jacks only, unlike the modulation oscillator on the Model 259, which has connections for both modulation (banana jacks) and audio (tini-jack). The smaller size of the 258, as well as the two types of FM for both oscillators makes this a prime candidate for auxiliary or main tone generator duties within a large or small DON B oriented 4U system.