The possibility is considered of controlling the intensity of a longitudinal electric field and the electron temperature in a decaying gas-discharge plasma. It is proposed to feed the discharge from a simple circuit that makes possible the control of the electric field in wide dynamic and frequency ranges. The procedure for controlling the field intensity and the electron temperature is experimentally investigated in the afterglow of a discharge in neon at pressures 2-30 torr and currents 10-100 mA. The possibility of arbitrarily varying the electron temperature can be employed to investigate the temperature dependences of the constants of the elementary processes that take place in a decaying plasma.