Reliable Automatic Sprinkler Co., Inc. has announced the availability of its PrePaK 4" and 6" Single and Double Interlock Preaction Systems. Single or double interlock option can be chosen by a simple code change on the programmable panel. The PrePaKs feature a 7 to 10 psi air pressure range for either single or double interlock preaction. The 1 1/2", 2 1/2", 4" and 6" PrePaKs are UL Listed and cUL certified. Reliable Automatic Sprinkler Co.