Autoradiopuhelin

ARP (Autoradiopuhelin, Car Radio Phone in English) was the first commercially operated public mobile phone network in Finland. The technology is that of zeroth generation (0G), since although it had cells, moving between them was not seamless. The network was proposed in 1968 and building began in 1969. It was launched in 1971, and reached 100% geographic coverage in 1978 with 140 base stations. ARP network was closed at the end of the year 2000 along with NMT900.

ARP was a success and reached great popularity (10800 users in the year 1977, 35000 in 1986), but finally became too congested and was gradually replaced by more modern NMT technology. However ARP was for a long time the only mobile phone network with 100% percent coverage and it remained popular in many special user groups.

ARP operated on 150 MHz frequency (147.9 - 154.875 MHz). Transmission power ranged from 1 watt to 5 watts. It used half-duplex transmission, meaning that receiving and transmitting voice could not happen at the same time. Being analog, it had no encryption and calls could be listened to with scanners. It started as a manually switched service, but was fully automated in 1990 although by that time the number of subscribers had dwindled down to 980 users. ARP did not support handover, so calls would disconnect when moving to a new cell area. Cell size was approximately 30 km.

ARP mobile terminals were extremely large for the time and could only be fitted in cars' trunks, with a handset near the driver's seat. ARP was also expensive.