carrier current service was called Drahtfunk, and in Switzerland Telefonrundspruch. In the Soviet Union, this approach was very common beginning in the 1930s because of its low cost and accessibility, and because it made reception of uncensored over-the-air transmissions more difficult. In Norway radiation from power lines was used, provided by the Linjesender facility. In Britain such systems were used for a time in areas where reception from conventional BBC radio transmitters was poor. In these systems programs were fed by special transformers into the lines. To prevent uncontrolled propagation, filters for the service's carrier frequencies were installed in substations and at line branches. Systems using telephone wires were incompatible with ISDN which required the same bandwidth to transmit digital data. Although the Swiss and German systems have been discontinued, the Italian :it:Filodiffusione still has several hundred thousand subscribers. Programs formerly carried by "wire broadcasting" in Switzerland included: 175 kHz Swiss Radio International 208 kHz RSR1 "la première" (French) 241 kHz "classical music" 274 kHz RSI1 "rete UNO" (Italian) 307 kHz DRS 1 (German) 340 kHz "easy music" Low-power broadcasting stations Carrier current technology is also used for broadcasting radio programs that can be received over a small area by standard AM radios. This is most often associated with college radio and high school radio, but also has applications for hospital radio stations and at military bases, sports stadiums, convention halls, mental and penal institutions, trailer parks, summer camps, office buildings, and drive-in movie theaters. Transmitters that use carrier current are very simple, making them an effective option for students interested in radio. Carrier current broadcasting began in 1936, when students at Brown University in Providence, Rhode Island developed a carrier current station initially called "The Brown Network". This station was founded by George Abraham and David W. Borst, who had originally installed an intercom system between their dormitory rooms. The intercom links were first expanded to additional locations, and then the system was replaced by distributed low-powered radio transmitters, which fed their signals into various buildings' electrical wires, allowing nearby radio receivers to receive the transmissions. The carrier current station idea soon spread to other college campuses, especially in the northeastern United States. The Intercollegiate Broadcasting System (IBS) was formed in February 1940, to coordinate activities between twelve college carrier current stations and to solicit advertisers interested in sponsoring programs geared toward their student audiences. The innovation received a