Normal Status

The “normal” status for a switch is the status its electrical contacts are in under a condition of
minimum physical stimulus. For a momentary-contact pushbutton switch, this would be the status
of the switch contact when it is not being pressed. The “normal” status of any switch is the way
it is drawn in an electrical schematic. For instance, the following diagram shows a normally-open
pushbutton switch controlling a lamp on a 120 volt AC circuit (the “hot” and “neutral” poles of the
AC power source labeled L1 and L2, respectively):

We can tell this switch is a normally-open (NO) switch because it is drawn in an open position.
The lamp will energize only if someone presses the switch, holding its normally-open contacts in the
“closed” position. Normally-open switch contacts are sometimes referred to in the electrical industry
as form-A contacts.

If we had used a normally-closed pushbutton switch instead, the behavior would be exactly
opposite. The lamp would energize if the switch was left alone, but it would turn off if anyone
pressed the switch. Normally-closed switch contacts are sometimes referred to in the electrical
industry as form-B contacts. :