Introduced by Sylvania in 1939 (and used mostly by Philco), this valve was the product of adding a suppressor grid to type 7B8, which was the loctal version of type 6A7. Adding the suppressor allowed Sylvania to lower the current of the 6.3-volt heater from 320 milliamperes[2] to 150 milliamperes[3] while maintaining the same conversion transconductance (550 microsiemens). This allowed Philco to use this valve in every line of radio throughout the 1940s.