This is another interesting alternate on/off circuit which combines AND gate and inverter. A brief definition of what logic gates are has been given in my alternate on/off circuit using logic inverters. Also given, description of a logic inverter with true table. Here we would quickly look at AND gate which is a new component in this circuit using its true table. AND gate has two or more inputs and one output and acts in the same way like a logical AND operator. That is if any of the inputs is '0', the output is '0'. All the input must be '1' for output to be '1'. SN74AHC1G08 and SN74AHC1G14 are singe AND gate and inverter respectively that you can use rather choosing from the popular CMOS IC 4000 series that have quad and hex gate in single IC respectively. Below are symbol of AND gate and the true table.

IN1 
IN2 
OUT 
1 
1 
1 
1 
0 
0 
0 
1 
0 
0 
0 
0 
AND gate true table 
The circuit triggering operation is the same as that of logic inverters. At the instance of power up, A is '0', it implies that '0' and '1' are the two logic level inputs this results in output '0' at B. B is the input to logic inverter, therefore C is 1 and the capacitor charges up via the 33K resistor. When the switch is pressed, logic level '1' is applied to A, this makes the inputs to the AND gate to be '1s' which makes B to be '1'. As B is '1', C is '0' and the capacitor discharges completely to '0'. When the SW is pressed the second time, '0' is applied to A and the process above is repeated.

A 
B 
C 
Power up 
0 
0 
1 
1st trigger 
1 
1 
0 
2nd trigger 
0 
0 
1 
3rd trigger 
1 
1 
0 
Table describing the circuit 
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Alternate on/off circuit
Alternate on/off circuit using 2 logic INVERTERs
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