From the manfacturer:

The CLIK64-P Series of battery-operated transmitters are wireless radio controls designed to be used with the CLIK64 Series of receivers. The CLIK64 transmitters use a very high level of security encryption to ensure the users identification code cannot be copied to gain unauthorized access to restricted areas. No coding switches are on the device. All programming credentials are factory set to ensure no duplication of identification codes.

A 3-volt lithium battery CR2032 powers the transmitters. The batteries should last up to 3 years with normal use. To conserve battery life, an internal timer limits the transmission duration to a few seconds if the button is pressed for a long period of time. Simply release the button and press again to transmit.