The ETL Mark IV B was developed by Nishino Hiroji, Fuchi Kazuhiro and others as a computer specifically for input/output. It was completed in February 1961. This was a transistor-based computer specially for input/output, which employed the technique of automatically interrupting programs, and it controlled 4 magnetic tape units. At the end of 1961, it was connected with the ETL Mark IV A (as shown in the photo). Today, some logic circuit plug-in cards from this machine are preserved at the National Institute of Advanced Industrial Science and Technology.