I have two telephone system in two buildings, the distance between them is 30 meters
First type Panasonic KX-TD1232 with 48 internal line
The second type Panasonic KX-TEM824 with 24 internal line
Can the two systems be linked and how? Residents can communicate with each other in the two buildings

if you have 1 co and 1 slt port on each system, put 1 fxo port in fron 1232 and have the fxs port on other end connect to line port
do the reverse on the second unit

I have used 2 Cisco SPA3102, one on each end, setup to pickup the extension on one side when picking up co port on the other.

if you have 2 of these units on each side you can have direct dial from extension to extension on each side

you can also set it for when you ring the slt extension, it will ring the co on the other side, easiest way to transfer calls if you don't have reverse polarity or cpc on your system