Pion electroproduction off the proton is analyzed in a new framework based on a general parametrization of transition amplitudes, including constraints from gauge invariance and threshold behavior. Data with energies $1.13~{rm GeV}<W<1.6~{rm GeV}$ and $Q^2$ below $6~{rm GeV}^2$ are included. The model is an extension of the latest Julich-Bonn solution incorporating constraints from pion-induced and photoproduction data. Performing large scale fits ($sim10^5$ data) we find a set of solutions with $chi^2_{rm dof}=1.69-1.81$ which allows us to assess the systematic uncertainty of the approach.
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