The 2633-232 and 2633-USB are wireless modems for use with the DewK Thermo-Hygrometer and the 2633-RF wireless option. The DewK can receive and respond to commands from a remote computer through a radio-frequency wireless link. The wireless link requires an RF modem be connected to the computer. Two different connection options: RS-232 (2633-232) or USB (2633-USB) RF interface using the 802.15.4 standard (basis for ZigBee) Operates in the license-free 2.