Low voltage cable can be buried to a maximum of 6 inches (15.2 cm). If necessary to splice cable, carefully follow instructions that came with the connector you have purchased. Do not use cable smaller than listed in chart below. SELECT CABLE.
https://images.homedepot-static.com/catalog/pdfImages/26/269c2ba7-98bf-4245-a0bc-32b70ad7ced1.pdf

