This circuit is from the time when cars used contact breakers. This 80's version measures the dwell angle of the contact breaker for dwell adjustment using an era integrated circuit, the LM3917.
This simple megaphone is from old documentation, but uses still current components. The circuit is...
August 2016 - It can be obtained from Mouser Electronics Mikromidia of the MikroElektronika...
May 2017 - In stock at Mouser Electronics DGD Dgate drivers from Diodes Incorptrated ara...