They interconnect through a compatible Fire Alarm Control Panel. There are many different types of sensors that can be installed on the same initiating device circuit. Compatible sensors will be listed in the paper work or on the manufacturers website of the control panel being used.
Whether or not you can use them depends on what type of circuit they are on. These are designed to work with a low voltage alarm system only. If you already have an alarm, they can be used with or in place of ionization detectors. Photoelectric units need visible smoke to alarm, so they are less likely to false than ionization units, but they trip later in the fire stage. Most ionization detectors are 110 volt (household power). You can only use 110v on these circuits. If you have 110v ionization detectors that are falsing, there are photo smokes available, just make sure they are compatible with your existing interconnected units, or replace all at once.