* source EXERCISE 6-2
R_R1         V1 0 6k 
R_R3         N00452 N00394 1k 
R_R2         V2 0 1k 
R_R4         N00606 N00556 3k 
C_C1         N00452 V1 30u 
X_s1         N00394 N00606 N/O_switch PARAMS: to=1
V_V1         N00394 V2  DC 40
V_V2         N00556 0  DC 12