Absolute charge-transfer cross-sections for collisions of protons with hydrogen and deuterium atoms have been measured within the energy range .1 eV to ISO eV using the merging-beams technique. The results are in excellent agreement with a fully quantum mechanical treatment of this reaction. In addition, cross sections for resonant charge transfer of helium ions and neutrals have been measured within the energy range 4 meV to 1 eV. These data show good agreement with the available theory. The experimental technique and apparatus are reviewed briefly and a discussion of the use and implementation of a CAMAC based microprocessor as an aid greatly facilitating experimental diagnostics is included.