Ambient Weather WH2C Wireless Thermo-Hygrometer Compatible with the Ambient Weather WS-0101, WS-1171, WS-1172, and WS-1173 weather stations. The WS-0100 and WS-0101 supports up to three remote channels. 2 "AAA" batteries (not included). Lithium recommend for long life and cold weather Includes 1 year Ambient Weather warranty.