Let’s look at this simple electropneumatic circuit. We have four rungs in the ladder diagram. In the first rung, a normally open push button, PB1, energizes Control Relay 1 (CR1) when pressed. The second rung features another normally open push button, PB2, which energizes Control Relay 2 (CR2). The third rung contains a normally open contact of CR1 and a normally closed contact of CR2, which controls Solenoid 1 (Sol1). When CR1 is energized, Soll activates, shifting the 5/3 valve to extend the