I am trying to simulate the circuit in ngspice, but it seems that the oscillation will not initiate. I delayed the on pulse, but the expected 20Hz square wave does not appear. I have spent an inordinate amount of time just because I am old stubborn. I might just have to build it first, but I am rearranging my stuff. Thanks a lot for your help. Note: the V1 pulse brings up the power supply after the simulation starts. Circuit with a generic 555 timer. Circuit description from ICM7555.