4.16 The circuit of Fig. P4.16 can be used in a signalling sys-

tem using one wire plus a common ground return. At any

moment, the input has one of three values: +3 V, 0 V, -3 V.

What is the status of the lamps for each input value? (Note

that the lamps can be located apart from each other and that/nthere may be several of each type of connection, all on one

wire!)

(+3V

V-20

L-3 V

0

Figure P4.16

D, Z

red

D₂ Ideal diodes

+1₁

=

3-V lamps

green