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Obstetricians have expressed a wish for a simple and low-cost apparatus for monitoring the heartbeats of a fetus before and during birth. This paper describes a special type of amplifier that was built to satisfy this requirement. By transposing the low frequencies of the heartbeats to a higher-frequency region, some of the difficulties that would otherwise be encountered are avoided. This makes the device easy to build with noncritical circuits; it should be inexpensive to manufacture.