# Power Supplies

## Introduction

Direct current supplies of up to 12V which are required by solid-state circuits may be obtained from batteries of primary or secondary cells (for example, in mobile equipment). Fixed equipment is most conveniently served by a power unit which transforms, rectifies and smoothes the public 240V 50Hz supply, then converts this into the stable output required

Photo 6.1. Two common power supplies for amateur radio equipment. The one on the left is fixed at 13.8V DC output - the most commonly required output voltage. The unit on the right is variable 3-15V dc output and has metering of both the current and voltage.

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