This pulse bus transceiver 1665 D system building block consists of a green board surrounded by an aluminum frame and four blue plastic connectors. At one end the connectors are female and at the other they are male. On the board there are various resistors, transistors, and capacitors. There are also there are also 19 brown wires at the top of the board. The back of the board has a circuit printed in solder as well as a lettered grid.
Digital Equipment Corporation (DEC)
Printed on the solder side of the board at the insertion end
"Amphenol is stamped with this number into the blue plastic connectors on the the component side of the board
This number is stamped into the metal frame on the side of the block