The VMOS and DMOS developed into what has become known as VDMOS (vertical DMOS). John Moll's research team at HP Labs fabricated DMOS prototypes in 1977, and demonstrated advantages over the VMOS, including lower on-resistance and higher breakdown voltage. The same year, Hitachi introduced the LDMOS (lateral DMOS), a planar type of DMOS. Hitachi was the only LDMOS manufacturer between 1977 and 1983, during which time LDMOS was used in audio power amplifiers from manufacturers such as HH Electronics (V-series) and Ashly Audio, and were used for music and public address systems. With the introduction of the 2G digital mobile network in 1995, the LDMOS became the most widely used RF power amplifier in mobile networks such as 2G, 3G, and 4G.