... ) Twin, Three, Four (Circular) Cores laid up filled, where necessary, with suitable material PVC sheath ST-1 of IS: 5831 (General ... purpose). For Flat Twin with or without E.C.C., Flat Three Core, PVC sheath General Purpose ... ) Twin or Three Cores laid flat for Twin with E.C.C. the position of E.C.C. center in the same plan ...