The Tektronix 067-0596-00 Chopped Voltage Reference Calibration Fixture is a signal generator that produces an approximately square waveform that alternates between two precisely controlled voltages, "V1" and "V2".
The unit consists of three subsystems − a variable DC voltage source for V1, a variable DC voltage source for V2, and an astable multivibrator that drives the coil of a relay that switches the output between V1 and V2. Each of the three subsystems has its own floating power supply (isolated secondary) coming off a power transformer that they share.
The 067-0596-00 uses an Airpax A175 chopper to switch the output between V1 and V2.
The 067-0596-00 is specified as part of calibration procedure for the 141A.
Phil Crosby writes regarding 067-0596-00:
I'm pretty sure it was Steve Roth, one of the most intuitive designers I've ever worked with who designed the 067-0596-00. I'm cc'ing Chuck Barrows because around that time I went into the 7K group, so I missed a lot.
Chuck Barrows writes regarding 067-0596-00:
We needed something in a hurry to calibrate the 141 signal amplitudes. I did the first one at Charlie Rhodes direction, a ‘Friday afternoon project’. He insisted on things like an OG3 as reference. Pretty sure there was a much improved later unit.
John Addis writes regarding 067-0596-00:
The 141 was introduced in March 1969. The positive and negative voltage references for the 067-0596-00 are 11.7V temperature compensated Zener diodes, apparently with a ±10ppm/˚C temperature coefficient.