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Note that references are to IEC 60950 Third Edition 1999-04. Where the references in the Second Edition differ, they appear in parentheses.

REQUIREMENTS

The standard specifies additional requirements for equipment designed to be connected to telecommunication networks.

In addition to SELV, three types of telecommunication circuits within equipment are defined, TNV-1, TNV-2 and TNV-3.

Table 2G and Figure 2F (Table 19) of IEC 60950 define the insulation requirements between these different types of circuits.

TNV circuits must be separated from hazardous voltages by double insulation or by basic insulation, together with protective screening connected to the protective earthing terminal.

WIth the exception of permanently connected equipment or pluggable equipment type B, or other exceptions given in Clause 6.1.2.2, TNV circuits must  be separated from earth by insulation that withstands an electric strength test of 1.5kV in areas where the nominal supply voltage exceeds 130V ac, or 1 kV in other areas. In some Scandinavian countries TNV circuits must be separated from earth by supplementary insulation, based on the voltage in the primary circuit.

Accessibility to TNV circuits is restricted.

Leakage currents to a telecommunications network must not exceed 0.25 mA.

Equipment users must be protected from overvoltages on TNV-1 and TNV-3 circuits.

REFERENCES

Complete requirements are given in IEC 60950, clause 6.