A simple panel that permits the connection of MES lamps in parallel arrangements.   Small switches are used in various positions.

It is best to use MES lamps at about 1.5 to 3 volts and at about 50 to 100mA rating.  Teachers can choose their own lamps but it is important to see changes of brightness as connections are changed therefore it is important that all globes are the same rating otherwise changes in brightness will become meaningless.

The more modern LED indicators are not used because they do not change brightness in a predictable manner.  Filaments in lamps beheve better.

Brand : IEC