We now have The Magnetic Pulse Generators, The MPG1, shown below, is more powerful and has a longer continuous-operation time.

Bob Beck recommended sessions of 10 minutes in length, pulsing about every 5 to 6 seconds or so.  The MPG1/with AC adapter pulses roughly every 6 seconds or so, which doubles the amount of pulses you get in 20 minutes. 

World's most powerful at over 40 kilogauss Micro-Processor Controlled Top Quality Components used throughout Powered by 12 volt A/C adaptor Unique High Efficiency Toroidal field coil Highly Flexible 2600 micro-strand Double Insulated cable Long continuous-operation times 6 second repetition rate Triple insulated Field Coil Professional grade Photo-flash Capacitor included in warranty