Fledermaus-Konverter (Ultraschall hörbar machen, mit BFO mischen)

Most electronic organs use multiple mechanical key contact assemblies, which can be eliminated by multiple electronic gates operated by a single key contact. Figure 1 shows the principle. KS is the normally closed contact. Figure 3 shows, as an example, three keyboard contacts each feeding a set of three organ stops. Resistors Rb define the tone balance and are determined when the organ stops are voiced.