Over a maximum of 4 km of Optical fiber cable (OFC) a Parabolic antenna "Bündelschlüsselgerät" (BSG 93) is connected to the SE. The optical signal has a user Bit rate of either 2 or 8 MiBit. The frequency range is from 14.64 to 15.21 GHz, with a frequency difference of at least 150 MHz. The maximum range is about 35 km. The range can be increase by using up to two R-905 as relay stations. A relay station consists of two R-905, which are connected to an optical fiber. Over an unencrypted service channel that is multiplexed to the utility and remote control signals can be telephoned with the other operators of the BSG93s and the SEs.