GLS combines a reed switch and a permanent magnet.

As shown in the following figure, two reeds of electromagnetic material are inserted opposite each other with a gap in a glass pipe. This section is the contacts. (Refer to Figure 1.)

When the permanent magnet nears this section, a magnetic field causes the two reeds to be attracted to the N pole and S pole. The contacts operate due to attraction, and the contacts switch. (Refer to Figure 2.)

Figure 1: Basic Construction of a Reed Switch



Figure 2: GLS Operating Principle