The 45-703 is a miniature microphone input audio transformer designed for building and replacement of transistorized audio equipment. It features a primary impedance of 200,000 O with 2.26 kO DC resistance and a secondary impedance of 1000 O with 43 O DC resistance, delivering a maximum power rating of 100 mW. The transformer employs high vacuum impregnation with a special protective coating on the coils and a hydrogen heat-treated alloy core to ensure high-quality audio performance. With a frequency response of ±3 dB from 20 Hz to 25 kHz and compact dimensions of 3/4" × 5/8" × 5/8", this transformer is ideal for microphone preamplifier stages and low-level audio signal conditioning in vintage and modern audio circuits.