A 2-Pack for the Same Door consists of two complete Doggie Doorbell packages. They are set to send signals on the same frequency. You can install one adapter on the inside and one on the outside. For most homes, only one receiver needs to be used. If you place the receiver in a central location, you should be able to hear it from anywhere in the house. Of course, you can use two receivers, for example, one placed upstairs and one downstairs. Each of the two adapters will trigger both receivers at the same time.
The 2-Pack for the Same Door can also be used for two doors as long as you don’t need to differentiate which door your dog is at by listening to the receiver’s sound. Both adapters will trigger the same receivers at the same time.
A Twin-Pack is similar to a 2-Pack, except that there is only one receiver.
A 2-Pack for 2 Doors consists of two complete Doggie Doorbell packages. They are set to send signals on the different frequencies. Each adapter will trigger its corresponding receiver. You can set the two receivers to different tunes. By differentiating the different tunes, you can tell which adapter has been triggered by your dog.
A 4-Pack for 2 Doors consists of four complete Doggie Doorbell packages. Two of them are set to send signals on the same frequency and the other two are on a different frequency. For each pair on the same frequency, you just need one receiver for most cases. They will both trigger that receiver. You can set the two receivers to different tunes. By differentiating the different tunes, you can tell which door your dog is at.
Any individual package from a multi-pack can function independently. If you find that you don’t need as many Doggie Doorbells as you previously thought, you can sell or give the extra ones to friends or use them at different locations, for example, your vacation home.
The frequency code is printed on a label on the receiver and the transmitter (inside the adapter). It is the single letter before the serial number. The code can be A or D. (B and C are discontinued.) The transmitter and the receiver from the same set should have the same frequency code. Multiple Doggie Doorbells on the set frequency code can work as a group. If you ever get confused which transmitter pairs with which receiver, you can simply match them by looking at the frequency codes. The color accent of the receiver is not related to the frequency code.