RCA 700-series conventional two-way radios. Other vehicular equipment had telephone handsets and rotary dials or pushbutton pads, and operated full duplex like a conventional wired telephone. A few users had full-duplex briefcase telephones (radically advanced for their day) At the end of RCC's existence, industry associations were working on a technical standard that would have allowed roaming, and some mobile users had multiple decoders to enable operation with more than one of the common signaling formats (600/1500, 2805, and Reach). Manual operation was often a fallback for RCC roamers. Other services In 1969 Penn Central Railroad equipped commuter trains along the New York-Washington route with special pay phones that allowed passengers to place telephone calls while the train was moving. The system re-used six frequencies in the 450 MHz band in nine sites. In the UK, Channel Islands and elsewhere the "Rabbit" phone system was briefly used, being a hybrid of "cell" base stations and handsets. One major limitation was that you had to be less than 300 feet (closer with buildings) from a base due to power limitations on a portable device. With modern technology a similar variant is being considered for Apple's new 4G "smart watch" so they can be used in large events in a broadly similar way to a femtocell. European mobile radio networks In Europe, several mutually incompatible mobile radio services were developed. In 1966 Norway had a system called OLT which was manually controlled. Finland's ARP, launched in 1971, was also manual as was the Swedish MTD. All were replaced by the automatic NMT, (Nordic Mobile Telephone) system in the early 1980s. In July 1971 Readycall was introduced in London by Burndept after obtaining a special concession to break the Post Office monopoly to allow selective calling to mobiles of calls from the public telephone system. This system was available to the public for a subscription of £16 month. A year later the service was extended to two other UK towns. West Germany had a network called A-Netz launched in 1952 as the country's first public commercial mobile phone network. In 1972 this was displaced by B-Netz which connected calls automatically. Cellular concept In December 1947, Douglas H. Ring and W. Rae Young, Bell Labs engineers, proposed hexagonal cells for mobile phones in vehicles. At this stage, the technology to implement these ideas did not exist, nor had the frequencies been allocated. Two decades