Velleman-Telephone-Amplifier-Kit-Velleman-K4900-Telephone-amplifier-kit-this-telephone-amplifier-may-be-used-as-a-free-standing-amplifier-with-speaker-isolation-transformer-interface-input-0-5W-8R-speaker-output-7-9V-AC-9-12V-DC-supply-suitable-for-audio-HIFI-applications-Velleman-K4900-Telephone-Amplifier-Kit