Velleman HAA2866 Programming & Installation Manual - page 44

43

APPENDIX

DRY CONTACT

A dry contact means that no electricity is connected to it. It is prepared for free connections. 

The Relay Output contacts provided in this keypad system are dry contacts.

N.C.

Normally Closed, the contact is closed circuit at normal status. It is open circuit when active.

N.O.

Normally Open, the contact is open circuit at normal status. It is closed circuit when active.

TRANSISTOR OPEN COLLECTOR OUTPUT

An open collector output is equivalent to a Normally Open (N.O.) contact referring to ground 

similar to a relay contact referring to ground. The transistor is normally OFF, and its output 

switches to ground (-) when active. The open collector can only provide switching function 

for small power but it is usually good enough for controlling of an alarm system. The Duress, 

Inter-lock and Key Active/Alarm Outputs of the keypad are open collector outputs.

OPEN COLLECTOR

OUTPUT ----

Output switches to

ground when activated

N.O. CONTACT

OUTPUT ----

Output switches to

ground when activated

EQUIVALENT