function out = KNaCl(V,I)
global E_Na E_K E_Cl
%
% 'N' resistor (i_1=K(V-E_K)), `S' resistor (V=Na(i_2)+E_Na), flat resister
% i_3 = Cl(V-E_Cl), all parallel to generate
% Spike Burster characteristics by Kirchhoff Laws so that I = i_1 + i_2 + i_3, or
% i_2 = I - i_1 = I - K(V - E_K) - Cl(V - E_Cl)
% E_Na -- Nernst potential for Na-channel (+55 mV)
% E_K -- Nernst potential for K-channel (-75 mV
% E_Cl -- Nernst potential for Cl-channel (-60 mV)
% 
out = V-Na(I - K(V-E_K) - Cl(V-E_Cl))-E_Na;