One gives characterizations of the dimension one complete equicharacteristic reduced noetherian local rings (R,m) with integral closure \((R',m')\) for which there exist coefficient fields k for R and \(k'\) for \(R'\) such that \(k\subset k'\) and \(R\otimes_ kk'\) is analytically unramified. The interest of these rings lies in the examples given by S. S. Abhyankar of irreducible curves to show that the notion of singularity of dimensional type 1 introduced by O. Zariski is specific to zero characteristic.