The SM-57 Tuning Meter is available as an accessory for use with the NC-57 as a tuning indicator and relative signal strength indicator. The SM-57 is fitted with a cable and plug for connection to the Accessory Connector Socket at the rear of the NC-57 and is contained in a metal case finished to match the Receiver. To utilize the SM-57 the following receiver control settings must be observed:

1. Control switch at A.V.C. or A.N.L.

2. R.F. Gain control full on.

Schematic of SM-57 Signal Meter.

Source: Instruction Manual for The National Model NC-57

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