Hitachi, Ltd.

Takuzi Mukaemachi

Shinzi Okuhara

Mitsuru Kawanami

Toshiaki Toyama

Taturu Miyoshi

A plurality of PNPN switches, each permitting current flow in either, i.e., positive or negative, direction, are arranged at the cross points between the rows and the columns of the speech paths so as to form a matrix. The gate trigger terminal of each PNPN switch is connected with a gating current circuit having a high impedance, which circuit is adapted to control ON and OFF operations of the switch. A plurality of means are provided to selectively turn the gate current circuits on and off so that gate current is supplied continuously for the gate terminal of any desired PNPN switch at least for the time during which the corresponding cross point of the matrix is to be electrically bridged.

Semiconductor channel switch

A transmission system comprising a network including cross-point switches arranged by four-layer semiconductor switching elements having self-holding function; an input connection circuit connected to the high potential side of a link of the network to supply the four-layer semiconductor switching elements with dc bias current for self-holding and including means to restrict the upper limit of the dc bias current and modulating means for superposing a signal to be transmitted on the dc bias current; a current control circuit connected to the low potential side of the link of the network and including a current switch circuit and an absorption type constant current circuit connected in parallel through a diode to the current switch circuit, both the circuits being so disposed as to permit the dc bias current from the high potential to the lower potential side of the link, and an output connection circuit, wherein, when the link of the network is to be closed, the current switch and the absorption type constant current circuit are activated thereby causing the four-layer semiconductor switching elements to be rendered conductive and then the current switch is rendered non-conductive, while the absorption type constant current circuit is rendered simultaneously to absorb the dc bias current.

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Yokohama, Japan

Takuzi Mukaemachi