GOST 18145-1981 Circuits at the interface C2 of the data transmission equipment with the terminals in the consequent data input-output. Nomenclature and technical requirements
GOST 25007-1981 Data transmission interface with communication channel transmission frequency separation system. Basic parameters at the interface
GOST 20855-1983 history
1983GOST 20855-1983 Data transimission system signal conversion modulus for switched and unswitched voice frequency channels. Types and basic parameters