This circuit, from a 1978 publication, uses a germanium power PNP, but the BD135 can be used for 6 V bells or buzzers with current up to 500 mA. The touch time is limited by capacitor C1 which can have values up to 4700uF. The diode can be 1N4148. Observe the polarity of the battery since the transistor is PNP.
