51
The Tektronix Type 51 is a sweep plug-in for 560-series scopes. It was introduced in 1961.
It provides a calibrated sweep speed of 5 ms/div, and a continuously variable magnifier that allows the sweep to be set within the range of 5 ms/div and 25 μs/div. Triggering can be set to automatic, at a specific level, or free-running. The 51 and the 50 are useful together for measurements in the audio frequency range.
