<P> The 1820s also saw the use of "portable death chambers" in Germany . A small chamber, equipped with a bell for signalling and a window for viewing the body, was constructed over an empty grave . Watchmen would check each day for signs of life or decomposition in each of the chambers . If the bell was rung the "body" could be immediately removed, but if the watchman observed signs of putrefaction in the corpse, a door in the floor of the chamber could be opened and the body would drop down into the grave . A panel could then be slid in to cover the grave and the upper chamber removed and reused . </P> <P> In 1829, Dr. Johann Gottfried Taberger designed a system using a bell which would alert the cemetery nightwatchman . The corpse would have strings attached to its hands, head and feet . A housing around the bell above ground prevented it ringing accidentally . An improvement over previous designs, the housing prevented rainwater from running down the tube and netting prevented insects from entering the coffin . If the bell rang the watchman had to insert a second tube and pump air into the coffin with a bellows to allow the occupant to survive until the casket could be dug up . </P> <P> The systems using cords tied to the body suffered from the drawback that the natural processes of decay often caused the body to swell or shift position, causing accidental tension on the cords and a "false positive". Franz Vester's 1868 "Burial Case" overcame this problem by adding a tube through which the face of the "corpse" could be viewed . If the interred person came to, they could ring the bell (if not strong enough to ascend the tube by means of a supplied ladder) and the watchmen could check to see if the person had genuinely returned to life or whether it was merely a movement of the corpse . Vester's design allowed the viewing tube to be removed and reused once death was assured . </P> <P> Count Michel de Karnice - Karnicki, a chamberlain to the Tsar of Russia, patented his own safety coffin, called Le Karnice, in 1897 and demonstrated it at the Sorbonne the following year . His design detected movement in the coffin and opened a tube to supply air while simultaneously raising a flag and ringing a bell . Le Karnice never caught on: it was too sensitive to allow for even a slight movement in a decaying corpse, and a demonstration in which one of Karnice - Karnicki's assistants had been buried alive ended badly when the signalling systems failed . Luckily, the breathing tube had activated and the assistant was disinterred unharmed, but the reputation of Le Karnice was damaged beyond repair . </P>

Where did the expression dead ringer come from