and earth (or T and E) format has the circuit protective conductor (CPC or Cearth) uninsulated (bare) and of reduced diameter compared to the main cores. Green and yellow sleeving is sold separately, to be applied at the ends. The cross section on the main conductors is given first, and then the cross-section of the CPC. Standard UK metric twin and earth cable sizes 1/1 mm2 and 1.5/1 mm2 have solid conductors and CPC (primarily used on low power lighting or alarm circuits) 2.5/1.5mm2 has a solid CPC and may have solid or stranded conductors (primarily used for socket circuits, radial or ring circuit) 4/1.5 mm2 and 6/2.5 mm2 have stranded conductors and a solid CPC (fixed high power equipment or sub-mains) 10/4 mm2 and 16/6 mm2 have stranded conductors and CPC (fixed high power equipment or sub-mains) In older properties (pre-1970) cable with imperial sizes are found, sometimes without CPC. Mainland UK wiring regulations do not at present (BS 7671:AMD3) acknowledge twin and earth or flat TPS with a full sized and insulated (G/Y) earth conductor as a valid cable type, which may be awkward for contractors who work cross-border with the Republic of Ireland. Also available in smaller conductor sizes are versions containing three current-carrying conductors and a circuit protective (earth) conductor. These configurations are commonly used for applications such as switched light circuits, battery-backed emergency lighting which requires a switched and unswitched supply, extractor fans with a run-on timer which require a switched and unswitched supply, mains-powered interlinked smoke alarms, and central heating thermostats. There is an overall sheath of grey PVC (BS 6004), or white for low smoke compound (BS 7211), although prior to 2005 white PVC was also available. Republic of Ireland In the Republic of Ireland the situation is different from that in the UK. Prior to 2013 IS 201-4:2001 ( I.S. 201 part 4: PVC and Low Smoke Halogen Free Sheathed cables for fixed wiring) permitted both the UK style of twin and earth, and also a version with a CPC with a cross-section equal to that of the main conductors and insulated in green and yellow inside the full length of the cable. However, from 2013, the option for the uninsulated and reduced CPC has been removed from the standard IS 201-4:2013, and as such is no longer permitted in new installations in the Republic of Ireland. See also Tough rubber-sheathed cable