This document specifies requirements for, and constructions and dimensions of, single core cables, rated voltage Uo / U = 300 /300 V, of the following type: Unscreened (0,5 mm2 to 2,5 mm2 single core) These cables are rated for occasional thermal stresses causing ageing equivalent to continuous operational life at a temperature of 90 °C. For standard cables this is determined by the acceptance test defined in EN 50305, using accelerated long-term (5000 h) thermal ageing indicating a 110 °C/20 000 h temperature index. Should the customer require lifetime predictions this should be demonstrated based on the temperature index of the product as supplied by the manufacturer. The maximum temperature for short circuit conditions is 160 °C based on duration of 5 s. Under fire conditions the cables exhibit special performance characteristics in respect of maximum permissible flame propagation (flame spread) and maximum permissible emission of smoke and toxic gases. These requirements are specified to permit the cables to satisfy Hazard Level 3 of EN 45545-1 and "2. prEN 50306-2:2018 should be used in conjunction with prEN 50306-1:2018, General requirements.