To help deter theft or misuse, this tamperproof alarm emits a piercing signal when a fire extinguisher is removed from its normal position. “Stop” sign design discourages wrongful use. This Wireless Alarm requires 4-Channel Receiver No. 16D855 or 8-Channel Receiver No. 16D856, sold separately. Mount the wireless alarm up to 1000-ft., line-of-sight, from wireless receiver.