Switching device for a telephone set with handset, switching an auxiliary device by substituting for the handset

A switching device for connecting an auxiliary device to a telephone set having a handset, said auxiliary device thereby replacing said handset which is disconnectable from the telephone set, the telephone set having a housing, the switching device having a casing said switching device comprising first connecting means for electrically connecting said telephone set to said switching device, second connecting means for electrically connecting said handset to said switching device, third connecting means for electrically connecting said auxiliary device to said switching device, and the switching device casing being entirely separate from the telephone set housing, the switching device casing including switching means having two switching states for mechanically receiving said handset when said handset is lifted off said telephone set housing, said switching means electrically switching from a first switching state in which only the handset is electrically connected to said telephone set through said first connecting means and second connecting means, to a second switching state in which only said auxiliary device is electrically connected to said telephone set through said first connecting means and third connecting means in response to mechanical placement of said handset on said casing of said switching device.