A highly reliable annunciator circuit which is immune from spurious signals generated in an elevator environment is provided. The circuit employs an input condition verification network which performs in conjunction with low true logic two-bit inputs by carrying out switching only when those inputs fall below a preset control value, highly enhanced performance is achieved. Volume control over the piezoelectric output developing a chime or gong sound is achieved through a variable impedance control which is adjustable on site.
5160913 - Electric horn with solid state driver - Owned by Sparton Corporation (Jackson, MI) [*] Notice:The portion of the term of this patent subsequent to September 17, 2008 has been disclaimed.
An electric horn having a diaphragm connected to a ferromagnetic plunger is driven by an electromagnetic coil to cause vibrations of the diaphragm at the resonant frequency of the diaphragm and plunger combination. A solid state driver has a timer tuned essentially to the frequency of the diaphragm assembly and controls the driver power output to effect coil energization to drive the diaphragm movement synchronously with the timer frequency. The driver output stage comprises a power MOSFET or a Darlington pair.
An electric horn having a diaphragm connected to a ferromagnetic plunger is driven by an electromagnetic coil to cause vibrations of the diaphragm at the resonant frequency of the diaphragm and plunger combination. A solid state driver has a timer tuned essentially to the frequency of the diaphragm assembly and controls the driver power output to effect coil energization to drive the diaphragm movement synchronously with the timer frequency. The driver output stage comprises a power MOSFET or a Darlington pair.
