Hardwired smoke detectors wiring

I think I know the answers to this, but I am not sure.
I have a building that already has 3 interconnected 120-volt smoke detectors. I want to add two more to the system. I want them to all be interconnected so that if one goes off, they all go off. This is just a 120 VAC interconnected system with no battery backup.
To install one of the new detectors, I am planning on opening up the junction box for nearby existing detector, and from there run 14/3 wire to the new detector. And, where the 14/3 wire from the new detector comes into the existing detector junction box, I would just connect red to red, white to white, and black to black.
To install the second new detector, I am planning on opening up the junction box for a different nearby existing detector, and from there run 14/3 wire to the new detector. And, where the 14/3 wire from the new detector comes into that existing detector junction box, I would just connect red to red, white to white, and black to black.
Is that correct in terms of the wiring?
Also, if I cannot find two new detectors that are the same model or compatible with the 3 existing detectors, I will just buy 5 new detectors and use them.
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On a smoke circuit it is normal for the red wire to be used for the inter-connect but make absolutely sure that is how yours are wired. The pigtail wires with the smoke connection plug are usually black white and yellow.
Many models are compatible so you may not need to buy all new but if they are more than 5 years old I would buy all new with battery back-up.
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Colbyt wrote:

Thanks. Do 120-volt smoke detectors with battery backup just have a a battery in each one? If so, and the power goes off, does that just change all of the smoke detectors to individual detectors with no interconnectivity feature?
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Mine use a common motorcycle-type battery- Yuasa NP7-12. -----
- gpsman
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you have an actual fire alarm panel in your house?
nate
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One 9 volt battery per unit. Last 2 years with no power off. Recommended change is yearly for the batteries.
I think and I want to stress the word think, that it still sounds off all the ones with a good battery. The voltage for the inter-connect is very low.
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