This unit can be used as is as a standalone keypad, or for parts. To be used as a hands-free telephone entry system it must be used in conjunction with other parts. It is called a “lobby panel“. Lobby panels can only be used with the 1816 or 1820 Telephone Intercom Systems. They are not Stand-Alone units so cannot be connected directly to a central office phone line.
Here’s the manual for details: https://gatedepot.com/amfile/file/download/file/42918/product/27883/
If you’re looking for a low price on a high quality keypad, I don’t want to use the telephone entry system, But need a high-quality keypad for your gate or door, it’s a great deal on the highest quality unit. I’m selling it for less than a Door King keypad sells for.
This unit sold new as it for over $800. This unit is brand new in the box and has never been installed.