M12 A-Code Connector Inter-changeability
To put it another way, what is the difference between 3, 4, 5, 8 pole connectors?
First of all let’s clarify one important point the 3, 4 and 5 pole connectors are all interchangeable, the 8 and the newer 12 pole are not!
If you look at the end of the female connector you will always see 5 cavities where in the 3 pole version there are only 3 contacts used (1, 3 and 4) and similarly for the 4 pole (1, 2, 3 and 4). The 8 pole however is totally incompatible with these versions due to the higher number and size of contacts used in this version.
The 3, 4 and 5 pole are inter-changeable so that you do not have to use a cable where are not using all of the functions of the device that it is connected to. One example being the programming input for some photo-electric sensors is on pin 5, if you are not using it then there is no need to have it connected.