Equations are derived which describe the terminal behaviour of the uncontrolled resistance-inductance fed bridge convertor. Generalisation of these equations to the controlled case is accomplished by a substitution of variables. Boundaries within which the uncontrolled rectifier can operate are specified. Plots of the terminal characteristics for the uncontrolled case visually show the approximation involved when the resistive portion of the commutation impedance is neglected. Simple approximations are provided for the fundamental current component equations which are derived.