HunterWireless Rain Clik TRANSMITTER ONLY

My old Rain-Clik was made in 2010. Will this work or do I need to buy a whole new sensor and receiver?

What does the date code on the box mean? is that the expected battery life? the sell by date? warranty coverage date? please clarify.

Mine is only 3 years old but the disks don't seem to expand enough to trip the sensor. Everything else checks out. Can I buy replacement disks?

Is it adjustable and what is its range in inches.