This circuit, published in 1978, has an interesting function. In the 2 V test position, the circuit only indicates current when the voltage of the battery under test is greater than 1.4 V and in the 12 V position, it only indicates when the voltage is greater than 10 V. The trimpots, which can be of 4k7, adjust the instrument's scale background. A 1.4 V zener can be used instead of B1.
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