The term High Data Rate(HDR) was used in the 1980s for data transmission ratesin fixed networks. The designation was not precisely specified and was in contrast to the Low Data Rate( LDR) with data rates of less than 64 kbit/s. In general, HDR data rates were assigned values that were higher than the basic ISDN data rate of 64 kbit/s at that time. In other documentation, High Data Rates were those above the primary multiplex rate of 2 Mbit/s. The classification according to the HDR rate in fixed networks is no longer relevant, since data rates have increased many times over in the meantime.