531

The Tektronix 531 is and oscilloscope that was made from the late 1950's through the early 1960's. It accepts letter-series and 1-series plug-ins. There is also a rack-mount version, the Tektronix RM31A. The RM31A has a sliding chassis so that the scope can be serviced without removing it from a rack.

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  RM31A