There was a Western Electric 400E line card. An article entitled"Advances in the 1A2 Key Telephone System", in the October 1970 Bell Laboratories Record, has a photo of the Western Electric 400D and the Western Electric 400E side by side.They had reduced the number of components from 41 to 17. This was done by replacing the transistors and all the components on the small secondary circuit board with an integrated circuit chip. It must not have worked out because in the early 70's the BSP for the 400 series noted the 400E Manufacture Discontinued.