What is the frequency? 

The frequency for the LM172 is 433.92 Mhz 

What is this compatible with? 

The LM172 is compatible with ALEKO swing gate openers AS/GG Series 450/600/650/850 900/1200/1300/1700 models, 
sliding gate openers AC 1300/1500/1700/2200/2400/2700/5700 and AR 900/1350/1550/1750/2250/2450/2750/5750 Series. 
also compatible with LockMaster LM902 LM901 Swing Gate Openers and DSC DSR SCG/SFG(H Model only) Sliding Gate Openers bought after July 2011. 

Does this have a backlit keypad? 

It has LED blacklight keys. 

What batteries does this take? 

The LM172 takes 3 AAA batteries. 

Should this be installed inside or outside the gate? 

The keypad should be installed outside the property, so on the outside of the gate. 

How far away can the keypad be from the control box? 

It should be positioned no more than 5 meters (16 feet) from the control box. 

What happens if the keypad is installed inside the gate? 

Electromagnetic waves from a passing vehicle may interfere with the operation of the keypad.