11. Consequently, the coherer cannot be relied upon as a " calling-up apparatus ". 12. Unfortunately, the reduction in the coherer 's electrical resistance persisted after the radio signal was removed. 13. This returned the coherer to the nonconductive state, turning off the electromagnet current, and the arm sprang back. 14. Popov constructed a filings coherer , one form of which was used in some surveying experiments by the Russian government. 15. Lodge used a detector called a " coherer ", a glass tube containing metal filings between two electrodes. 16. The receiver for the transatlantic demonstration employed a coherer , which had poor sensitivity and degraded the tuning of the receiver. 17. A coherer with electromagnet-operated " tapper " ( decoherer ), built by early radio researcher Emile Guarini around 1904. 18. However the usual range of coherer receivers even with the powerful transmitters of this era was limited to a few hundred miles. 19. The coherer became the basis for radio reception, and remained in widespread use for about ten years, until about 1907. 20. In 1894-95 he built his first radio receiver, an improved version of coherer -based design by Oliver Lodge.
