The present disclosure describes circuit variants for reducing electromagnetic interference from saturable core keyboards to acceptable levels. The invention finds particular application in conjunction with capacitive-discharge scan techniques used in such keyboards. In order to attenuate the external field resulting from such techniques, a circuit is taught which effectively disconnects the scan line array from the capacitor charging circuit during the time between scans. A second variant, when added to the first, further reduces interference by disconnecting the entire scan circuit from the supply potential during the scan time thereby eliminating steady-state currents and turnoff oscillatory transients.