Here's your truth table. I have highlighted in red the states where the
light will halt.
| Switch |
A(t) |
B(t) |
C(t) |
D(t) |
A(t+1) |
B(t+1) |
C(t+1) |
D(t+1) |
| 0 |
0 |
0 |
0 |
0 |
0 |
0 |
1 |
0 |
| 0 |
0 |
0 |
0 |
1 |
0 |
0 |
1 |
1 |
| 0 |
0 |
0 |
1 |
0 |
0 |
1 |
0 |
0 |
| 0 |
0 |
0 |
1 |
1 |
0 |
1 |
0 |
1 |
| 0 |
0 |
1 |
0 |
0 |
0 |
1 |
1 |
0 |
| 0 |
0 |
1 |
0 |
1 |
0 |
1 |
0 |
1 |
| 0 |
0 |
1 |
1 |
0 |
1 |
0 |
0 |
0 |
| 0 |
0 |
1 |
1 |
1 |
1 |
0 |
0 |
1 |
| 0 |
1 |
0 |
0 |
0 |
1 |
0 |
1 |
0 |
| 0 |
1 |
0 |
0 |
1 |
1 |
0 |
1 |
1 |
| 0 |
1 |
0 |
1 |
0 |
0 |
0 |
0 |
0 |
| 0 |
1 |
0 |
1 |
1 |
1 |
0 |
1 |
1 |
| 0 |
1 |
1 |
0 |
0 |
1 |
0 |
1 |
0 |
| 0 |
1 |
1 |
0 |
1 |
1 |
0 |
1 |
1 |
| 0 |
1 |
1 |
1 |
0 |
1 |
0 |
1 |
0 |
| 0 |
1 |
1 |
1 |
1 |
1 |
0 |
1 |
1 |
| 1 |
0 |
0 |
0 |
0 |
0 |
0 |
1 |
1 |
| 1 |
0 |
0 |
0 |
1 |
0 |
0 |
1 |
0 |
| 1 |
0 |
0 |
1 |
0 |
0 |
1 |
0 |
1 |
| 1 |
0 |
0 |
1 |
1 |
0 |
1 |
0 |
0 |
| 1 |
0 |
1 |
0 |
0 |
0 |
1 |
0 |
1 |
| 1 |
0 |
1 |
0 |
1 |
0 |
1 |
1 |
0 |
| 1 |
0 |
1 |
1 |
0 |
1 |
0 |
0 |
1 |
| 1 |
0 |
1 |
1 |
1 |
1 |
0 |
0 |
0 |
| 1 |
1 |
0 |
0 |
0 |
1 |
0 |
1 |
1 |
| 1 |
1 |
0 |
0 |
1 |
1 |
0 |
1 |
0 |
| 1 |
1 |
0 |
1 |
0 |
1 |
0 |
1 |
1 |
| 1 |
1 |
0 |
1 |
1 |
0 |
0 |
0 |
0 |
| 1 |
1 |
1 |
0 |
0 |
1 |
0 |
1 |
1 |
| 1 |
1 |
1 |
0 |
1 |
1 |
0 |
1 |
0 |
| 1 |
1 |
1 |
1 |
0 |
1 |
0 |
1 |
1 |
| 1 |
1 |
1 |
1 |
1 |
1 |
0 |
1 |
0 |
|