4-channel radio transmission module with interchangeable antenna. If needed, a FA250 radio antenna can be connected. Standby power loss is only 0.1 watts. This is a rail-mounted device for installation on a mounting rail (1TE). It connects to the Eltako RS485 bus. The power supply is cross-wired with a jumper. Alternatively, the power supply can be connected with a 12V DC switching power supply at the terminals +12V/GND. This radio transmission module has four channels and can send radio telegrams in the Eltako building radio system like a 4-channel radio switch. E1 triggers a radio telegram like pressing the top of a switch, E2 like pressing the bottom, E3 like pressing the top left of a double switch, and E4 like pressing the bottom left of a double switch. The telegram when opening the control contacts is identical to releasing the radio switch. Multiple radio transmission modules must not be activated simultaneously. The universal control voltage at +En/-E processes control commands from 8 to 253V AC or 10 to 230V DC with a minimum duration of 0.2 seconds. The maximum parallel capacitance of the control lines at 230V is 0.9 µF, which corresponds to a length of about 3000 meters. If terminals E1 and E2 are connected with a jumper, a radio telegram from E2 is sent once per minute as long as the control voltage is present, e.g., for central commands with priority. The rotary switch is needed to activate or deactivate the encryption and is set to AUTO during operation. To activate encryption: turn the rotary switch to the right stop (key position) and press once. To deactivate encryption: turn the rotary switch to the left stop (crossed key position) and press once.