Here is what one gets when one SCR is fired.
The other can only be fired if the voltage of its Vak is positive only ...

Here when SCR bis fired at n=3, see the Load resistor voltage (V4).

And when n=6

Here is what one gets when one SCR is fired.
The other can only be fired if the voltage of its Vak is positive only ...

Here when SCR bis fired at n=3, see the Load resistor voltage (VA).

And when n=6