An apparatus in the form of a toy building block, comprising: a first circuit board having a first exterior side surface, a second exterior side surface opposite the first side surface, a first end surface and a second end surface opposite the first end surface, the first exterior side surface and the second exterior side surface each being different than both the first end surface and the second end surface; a first connector fixedly mounted to the first circuit board such that an exterior surface of the first connector is aligned with the first end surface of the first circuit board,; and a second connector fixedly mounted to the first circuit board such that an exterior surface of the second connector is aligned with the second end surface of the first circuit board, a portion of the first exterior side surface of the first circuit board between the first connector and the second connector being visible during use of the apparatus by a user; the first connector including at least one first conductor configured to engage a second conductor on a third connector coupled to a second circuit board , the second connector including at least one third conductor configured to engage a fourth conductor on a fourth connector coupled to a third circuit board , characterized in that : the first connector includes a first housing comprising two magnets with surface poles exposed that act as a polarizing and locking element; and the second connector includes a second housing comprising one or more metal plates. a first circuit board having a first exterior side surface, a second exterior side surface opposite the first side surface, a first end surface and a second end surface opposite the first end surface, the first exterior side surface and the second exterior side surface each being different than both the first end surface and the second end surface; a first connector fixedly mounted to the first circuit board such that an exterior surface of the first connector is aligned with the first end surface of the first circuit board,; and a second connector fixedly mounted to the first circuit board such that an exterior surface of the second connector is aligned with the second end surface of the first circuit board, a portion of the first exterior side surface of the first circuit board between the first connector and the second connector being visible during use of the apparatus by a user; the first connector including at least one first conductor configured to engage a second conductor on a third connector coupled to a second circuit board , the second connector including at least one third conductor configured to engage a fourth conductor on a fourth connector coupled to a third circuit board , characterized in that : the first connector includes a first housing comprising two magnets with surface poles exposed that act as a polarizing and locking element; and the second connector includes a second housing comprising one or more metal plates. the first connector includes a first housing comprising two magnets with surface poles exposed that act as a polarizing and locking element; and the second connector includes a second housing comprising one or more metal plates. <EOS>