This unique prototype is not part of the museum exhibit but was brought into the museum by the owner Joe Burger.
This is the 1968 prototype for the MO18 channel switch IC, 155-0022-00. MO18 was the internal designation for the 50/450 process channel switch that can be found in the horizontal interface boards of the 7504, 7704, and the vertical interface board of the 7503. The interface boards are easily removed from the main interface boards of those instruments (a screw at the top and bottom of the interface board, accessible through the front the plug-in cage). We believe that all of the boards mentioned used a folded cascode differential PNP pair to drive the plug-in outputs. Also the vertical boards had trigger outputs that employed the same channel switches and PNPs. These 155-0022-00 parts were also used for the 7704 trigger channel.