Can you please help me connect my pool timer. I recently purchased a home with a swimming pool and the timer was not working (disconnected). I ordered the identical timer but there were no installation instructions just a schematic on the back side. The connection schematic is in the attachment and I tried to Google information but nothing seems to make it any clearer. There is an M, COMM, NC NO. Can anyone explain what these 4 mean. Like the original timer there are 5 terminals but I only have 4 wires. I assume power (black) gets connected to number 3, correct? I'm clueless on the others. HELP Please?

Aneta