These consist of a spiral wire tube covered with woven fabric, with a funnel-shaped mouth-piece at one end and an ear-piece at the other.  The mouth-piece should be held close to the lips of the speaker and the ear-piece made to rest lightly in the external auditory canal.  Curriers’ Cylindrical Conversation Tube was designed to extend the benefits of hearing to the deaf  or for business men who do not wish others to hear their conversation.  It was carried in the pocked to worn about theneck and was touted as the most powerful conductor of human voice yet perfected.