Sometimes it's critical to ensure one door is closed before the other one can open, creating a sort of 'air-lock' type setup, where you go through the first door but cannot go through the second door until you've fully closed the first door. This is particularly important in secure facilities, but has its uses in all sorts of environments.
The principle of this module is that you would have monitored locks on each door wired into this relay module, which allows the relay to determine if each door is fully closed or not. You would then have your keypads, card readers, or simple push-to-release buttons each side of both doors, which when triggered will send a trigger to the interlocking relay module. The module then checks to see if the lock monitor or door contact of the other door is currently showing the door as being closed, and if it is the relay will cut the circuit to the lock, allowing it to be released. But if the other door is not closed, then the lock would not be released. It really is that simple.
The module requires you to use normally-open contacts from the monitored outputs on the lock. So this needs to be a normally-open output when the door is closed, which changes to normally-closed when the door is open). If you already have electric locks and this is not an available feature, then you could source some door contacts for each door, and wire these in to the reed terminals on the module as per the wiring diagram. Just be conscious that most door contacts are normally-closed, and you'd need to avoid these and go for normally-open as described above. To assist you, we have listed some of the most popular monitored lock options available on the market, but of course every installation is different and has unique requirements, so this list is by no means exhaustive and you should consider all options before making your final decision.
The relay rating on these is suitable for pretty much every typical setup too - capable if handing 12-24v DC, rated at 6Amps @ 12v (so 3Amps at 24v) - you should never need to put more than this through for two doors, so whether you're using strike releases, electric multipoints, or the famously power-hungry Cisa electric locks, you shouldn't have any issues here.
It is worth noting, that this relay will only send the outward trigger to the lock for the duration of the trigger from the input (your card reader, keypad, or button etc). So bear in mind if you plan on using a momentary push-switch, then unless your chosen electric lock has a relocking time-delay feature, then the lock will re-lock as soon as your finger is off the button; so it's worth choosing an input method OR lock which has a time delay setting, to give you time to open the door after the pressing the button. Alternatively, you can use timer relays for your locks which will allow you to have them unlocked for a certain duration rather than for just the moment as you press the button.
But of course, most input devices such as keypads, card readers and so on, normally offer a release timer anyway, so it's only really when using a basic push-button that you need to be more considerate of the un-locking time issue.
The images show the product from different angles and the back has a self adhesive pad that can used to stick the PCB to a panel or similar.