The Tektronix Type 1A5 is a differential amplifier plug-in for 500-series scopes.
Bandwidth is 50 MHz down to 5 mV/div. The maximum differential sensitivity is 1 mV/div, with a bandwidth of 40 MHz. Common-mode rejection is 20,000 to 1 at low frequencies, deteriorating to 200:1 at 20 MHz.
Like most Tektronix differential plug-ins, it has three modes: VA-VC, VA-VB, and VC-VB. VC is controlled by a ten-turn potentiometer and can vary from -5 V to +5 V (0.5 V on the 5 V/div to 20 V/div ranges).please add