Which do you need? Normally Closed or Normally Open Holder...
As a standard, the "Normal" position refers to the holder when there is NO Handpiece or Instrument resting in the holder.
Air/Water Activated Normally Closed (N/C) Holders:
When the handpiece is removed from the holder, the air signal stops. This relieves the air pressure off of the control block. Air and/or water will then be allowed to flow through the ports when the foot control is pressed. The N/C holder is used in the automatic delivery systems and is the most common in the industry.
Electric Activated Normally Closed (N/C) Holders:
When a handpiece, or similar instrument, is removed from the holder the momentary switch goes to its normally closed position. This now completes the circuit and allows current to flow to the relay, or control circuit. In dental equipment applications this usually means the instrument or piece of equipment, is in an operation or “ON” mode.
Normally Open (N/O) Automatic Air Activated Holders:
When the handpiece is removed from the holder, the air flows through sending an air signal to actuate. Newer A-dec(R) and Proma(R) units use this type of automatic handpiece holders and also used for Accessory instruments.
