  The properties of Josephson devices are strongly affected by geometrical
effects such as those associated with the magnetic field induced by the bias
current. The generally adopted analysis of Owen and Scalapino [{\it Phys.
Rev.}{\bf 164}, 538 (1967)] for the critical current, $I_c$, of an in-line
Josephson tunnel junction in presence of an in-plane external magnetic field,
$H_e$, is revisited and extended to junctions whose electrodes can be thin and
of different materials. We demonstrate that the asymmetry of the magnetic
diffraction pattern, $I_c(H_e)$, is ascribed to the different electrode
inductances for which we provide empirical expressions. We also generalize the
modeling to the window-type junctions used nowadays and discuss how to take
advantage of the asymmetric behavior in the realization of some superconducting
devices. Further we report a systematic investigation of the diffraction
patterns of in-line window-type junctions having a number of diverse
geometrical configurations and made of dissimilar materials. The experimental
results are found in agreement with the predictions and clearly demonstrate
that the pattern asymmetry increases with the difference in the electrode
inductances.
