Figure 4.11. For a sighted person the physical layout of a schematic drawing can either convey or obscure information depending on how it is laid out. In figures 4.11 and 4.12 the electrical connections are identical but the layout is quite different. Figure 4.11 conveys how the equivalent circuit takes the place of the transistor but it would be hard to visualize how the loop equation is written. In figure 4.12 the correspondence between the transistor and the equivalent cirrcuitis not as clear but the loop for summing the voltages is obvious. An attempt will be made to convey this information in words. The equivalent circuit from figure 4.7 has been dropped whole into this circuit. It will be described again here so you don't have to refer back to it. There are two terminals on the left and two on the right. The bottom terminals on both sides are connected together and both are labeled with the letter E. The top terminal on the left is labeled B and there is a resistor connected from the B terminal to the E connection. This resistor is labeled h sub I e. On the right the C terminal connects to one end of an ideal current source. The other end of the source connects to the E connection. The arrow indicates that current from the source flows from C to E. The current source is labeled I sub b times h sub f e. This is a subsection of the diagram. There are other schematic symbols to the left of, below, and to the right of, this subsection. Note that neither E terminal connects to ground. On the left is an AC generator with one end going to ground. The other end connects to the B terminal. The generator is labeled V in. On the right a resistor has one end connected to the E terminal on that side. The resistor goes down and the other end connects to ground. This resistor is labeled R L. A line from the ground point goes to the right past RL and once clear of it turns upwards. When this line reaches the same level as the C terminal it turns to the left and connects to the c terminal. The c, collector, is grounded by this connection. End verbal description.