The Bendix two-way (TW) series valves are manually operated, non-graduating, on-off valves. They are extensively used in air systems to control nonmodulating air controlled devices. They may be lever or button operated, direct or remote control. The Bendix® TW‑4™ valve is a manually operated, non‑graduating on‑off valve used in air systems to control non‑modulating devices. The plunger is designed for a push‑button, providing momentary application whenever the button is depressed.