Schematics question

Judging by the situation as described, where the photocell is active when the beam is present, it will be holding the relay open when energized and letting it close when the beam is broken- this would mean that the alarm should be fed, from it's power supply, through the NC and common leads. Since there may be some electronics present to change this, the simple solution is to take any pair, common + NC or common+ NO and try it. If it doesn't work as desired, when the beam is broken, try the other pair. It's an either/or situation.

I meant I think he device powers itself *and* the alarm..a power source did come with the device

Yes I do: I have installed panels and sub panels..light switch boxes and outlets; fans and lights from it. I made up my own 4 outlet receptacle for a long extension cord I use when I play in my band at functions. Yes I can splice and dice. Yes I have some knowledge. I guess from now on when I ask a question I need to put my resume, basic though it is :-)

My question is not on how electricity works. It's about reading a schematic and how to follow it You should have sent me this:

Cool, then you won't have to worry about getting a power supply.

Good to know, and this is something you should have stated from the get go.

On your desk/workbench you may:

Hook up the power supply to the sensor.

Face the sensor at a reflective surface, or the beam reflector that should have come with the unit, making sure that there is a couple of feet between the two.

Energize the power supply.

Set your meter for Ohm/continuity and place the red lead on the COM terminal, and the black lead on the NC terminal. Does it show zero Ohms or continuity? While holding the test leads on the terminals with one hand, move your other hand in front of the sensor and block the beam for 1 second, then remove your hand from in front of the beam. Does the Ohms/continuity change?

Move the black lead to the NO terminal and place your hand in front of the beam as before. The meter readings should be exactly opposite from the previous readings.

The combination that does not show continuity when your hand is not blocking the beam, but does show continuity when your hand is blocking the beam, is the combination that you want to use.

Power goes in on the COM, and goes out on the NO or NC to the bell.

Power Supply (+) ====> COM

NC OR NO ====> (+)Bell(-) ====> Power Supply (-)

Some might have you "sink" the bell, but I won't go there...

Please let us know which state is normally closed with this device. Powered or unpowered. It might be a useful bit of information for someone in the future.

Hehe, that wasn't exactly how you presented your question. :)

Excellent!! Excellent response!! When I get over this flu I will do just that, and also write back on the results.. I will try to get a copy of the schematic up also, req

Getting ready to test the system ..the dc power supply has a plus, minus, then a M italic type symbol with an I on the top as if it was a whisk broom with a handles and someone was sweeping.. It is a short circuit protected power supply so I assume it's a ground of some sort...just want to be sure.. thanks

req

Ok so I called up a company inthe us for help..they said that the alarm has to be powered, so connect the - from the power supply to the com on the reciever, then from NC on reciever to alarm - . The + from power supply goes direct to + on alarm. Before I did all this I continuity tested the connection and it was closed..This meant that with the power on it would open the circuit, which it did when I powered up. So when beam is broken the circuit closes and alarm goes off. which it did when I connected the alarm. I used same power supply for all three and worked fine. So thanks to all for the responses I guess I'm done req