Power-saving device for a cable-information receiving/transmitting apparatus

Claim 1

A power-saving device for a cable-information receiving/transmitting apparatus, said cable-apparatus having an AC power line to connect to an AC-power source and a cable-terminal set to connect to said central office, said power-saving device having a first AC-terminal set to connect with said AC-power source, a second AC-terminal set to connect with said AC power line of said apparatus, a first cable-terminal set to connect with a cable from a central office, and a second cable-terminal set to connect with said cable-terminal set of said apparatus, said device starting the AC-power supply of said AC-power source to said apparatus in any of the following states: a. when ring signal arrive from said central office via said cable; b. when the handpiece of a telephone set attached to said apparatus is picked up; and cut off the AC-power supply of said AC-power source to said apparatus after a predetermined time in any of the following states: c. when a reception of information from said central office via said cable by said apparatus is over; d. when a transmission of information from said apparatus via said cable to said central office is over; said device being characterized by that it further comprises the following components: an AC-controlling means which has an AC-input end connected to said AC-power source, an AC-output end connected to said AC power line of said apparatus and a controlling portion, said AC-controlling means only allowing and AC current to be supplied from said AC source via said AC-input end and said AC-output end to said apparatus when said AC-controlling means is in activated state, said AC-controlling means being activated when a current is applied to said controlling portion; a transistor, of which the CE path is connected to said controlling portion of said AC-controlling means such that when a current passes through the CE path of said transistor, said AC-controlling means is activated; an optical coupler comprising a photoemitter and a photoreceiver, wherein said photoreceiver has two terminals which are respectively connected to the collector and the base of said transistor, so that when said photoemitter is actuated, said photoreceiver is activated to become conductive, thus activating said transistor; a tapping/rectifying circuit provided between the AC-input end of said AC-controlling means and said AC-power source to tap a current from said AC-power source and to rectify the tapped current and supply the tapped and rectified current to said photoreceiver, the base of said transistor, the CE path of said transistor and the controlling portion of said AC-controlling element; said component being so connected that said photoemitter is inaccessible by any current derived from said AC-power source and only accessible by a current from said cable.