Figure 3.15. There are two input terminals on the left and two output terminals on the right. The lower left input terminal connects to the bottom line of the circuit as does the lower right output terminal. The upper left input terminal connects to one end of a resistor labeled R sub eh. The other end connects to the cathode of a zener diode. The anode connects to the bottom line. The junction of the resistor and diode connects to the upper output terminal. End verbal description.