Home intercom telephone set

Claim 1

A telephone for use in an intercom system having a similar second telephone, the telephone comprising: a prefabricated unit comprising a supporting plate having upright web plates and further comprising electrical connecting lines including dimensionally stable wire stirrups having bentin ends extending through bores in said web plates to form a first, second and third pair of opposing contact pins; a case enclosing said electrical connecting lines and detachably secured to said supporting plate; a ringing unit electrically connected to said electrical connecting lines; a receiver having assembled therein a speaking unit comprising a microphone and a loudspeaker electrically connected to said electrical connecting lines, wherein said receiver is removably held by said case; means for connecting a current source to said electrical connecting lines; means for electrically connecting the second telephone to said electrical connecting lines; an electrically conductive selector device selectively movable into and out of contact with said first pair of opposing contact pins to establish or break electrical connection therebetween, wherein said selector device comprises a first spring element normally biased out of contact with said first pair of opposing contact pins; a ringing key for energizing the ringing unit of the second telephone when said ringing key is actuated, wherein said ringing key cooperates with said selector device to move said selector device against its normal spring bias and into contact with said first pair of opposing contact pins when said ringing key is actuated; an electrically conductive switching device selectively movable into contact with said second and third pairs of opposing contact pins to selectively establish electrical connection between contact pins of each said pair, wherein said switching device comprises a second spring element normally biased into contact with said third pair of opposing contact pins; and a reversing key having a first position for connecting said ringing unit into an electrical circuit including the selector device of the second telephone and a second position for connecting said speaking unit into an electrical circuit including the speaking unit of the second telephone when its reversing key is in the second position and for connecting said selector device into an electrical circuit including the ringing unit of the second telephone when its reversing key is in its first position, wherein said switching device and said receiver cooperate with said reversing key to move said reversing key into its first position when said receiver is held by said case and establish electrical connection between said second pair of opposing contact pins by moving said switching device against its normal bias and to move said reversing key into its second position when said receiver is removed from said case and establish electrical connection between said third pair of opposing contact pins by permitting said switching device to move according to its normal bias.