Described is a protective helmet comprising an impact-resistant outer helmet shell into which a head padding (10) is removably inserted as separate inner helmet shell. The protective helmet is provided with radiotelephone equipment. With the exception of a microphone and possibly an on/off switch and...http://www.google.com/patents/US5119505?utm_source=gb-gplus-sharePatent US5119505 - Protective helmet with removable protective lining for cushioning radio circuitry
