ferrite bead clamp
http://my-great-blog-7950.249104.n8.nabble.com/why-the-biggest-myths-about-emi-suppression-core-may-actually-be-right-tp6.html
The Emi Core is made up of ED Ef (Emitter Farad) and B+ at the output. In the input on the Emi Core the output impedance is often held low to scale back any feed-back difficulties. The BC235 is Generally utilised