This is a plug in module built around a U shaped metal rod which serves as frame, handle and guide pins. There are 2 metal plates attached across the frame. The rear plate has a pair of Amphenol 32 pin finger connectors. The front plate has 4 test points and 5 socketed vacuum tubes (3 miniature, 2 octal). A circuit board located between the front and rear plates has several rows of terminal posts. A variety of discrete components are soldered to the terminal posts on both sides of the board. The front plate has "LOOP WRITE" printed on it.