Guess.
Make sure they are all off first and turn them on one by one until you notice one that doesn't do any thing to your surroundings.
When switches or any circuit opening devices are in series with each other, they all have to be in the closed position to energize the load.When switches or any circuit opening devices are in parallel with each other, any one of the switches or circuit opening devices in the closed position will energize the load.
Circuit
A switches main purposes is to stop the current flow in a closed circuit.
Switches control the flow of electric current in a circuit. In an open circuit, the switch is off, interrupting the flow of current. When the switch is closed in a closed circuit, it allows the current to flow continuously through the circuit.
A switch in a circuit controls the flow of electricity by opening or closing the circuit. When the switch is closed, it allows electricity to flow through the circuit, and when it is open, it stops the flow of electricity. Switches are commonly used to turn devices on and off.
In order for the load to be energized in a circuit with multiple switches in series, all the switches must be closed or in the "on" position. This is because switches in series function like an "AND" gate in digital logic, requiring all inputs to be true for the output to be true. If any one of the switches is open or in the "off" position, the circuit will be open and the load will not receive power. Therefore, all switches must be closed to complete the circuit and energize the load.
it's bulb 3
The store is closed
An AND gate can be replaced by series switches by connecting multiple switches in series and closing all switches in the series circuit to activate the output. When all switches are closed (logic 1), the output will be high (logic 1), similar to the behavior of an AND gate which gives a high output only when all inputs are high.
POTS or PSTN
It refers to asystem whereby the loop of control is closed to outside interference.
To determine if a valve is open or closed, you can visually inspect the position of the valve handle or lever. If the handle is parallel to the pipe, the valve is open. If the handle is perpendicular to the pipe, the valve is closed.