Figure 5.4, Improved Simple Voltage Regulator Circuit. A transformer is shown on the left. The top of the secondary goes to the top AC connection on the bridge. The bottom of the secondary goes to the bottom AC connection. The negative output goes to common. The positive connects to the positive of C1. The negative of C1 goes to common. The positive of C1 goes to the collector of an N P N transistor, Q1. The emitter of Q1 goes to the positive output terminal of the power supply. The positive output terminal connects through R3 to the top of a pot, R4. The bottom of R4 connects through R5 to common. Common is the negative output terminal. The positive of C1 connects to one end of a resistor, R1. The other end of R1 connects to the base of Q1. The base of Q1 also connects to the collector of Q2, another N P N transistor. The base of Q2 connects to the wiper of R4. The emitter of Q2 connects to the cathode of zener diode D5. The anode connects to common. A resistor R2 connects between the positive output and the cathode of D5. End verbal description.