Signal isolating technique

Claim 1

Apparatus for transmitting a logic signal through a plurality of signal channels, comprising, a plurality of signal channels, input circuit means for applying a digital signal to said plurality of signal channels, each of said signal channels including: (a) an optical isolating circuit including a light emitting diode having an input and an output, said input corresponding to the input of said optical isolating circuit and having an electrical input lead connected thereto, the electrical input leads of the respective signal channels being connected in common to said input circuit means, (b) an electrical excitation means and a first electrical impedance means connecting said electrical excitation means to said electrical input lead, (c) a second electrical impedance means connecting the output of the light emitting diode to an electrical ground, the value of said first electrical impedance means being such as to isolate said electrical means from damaging current surges resulting from a component failure in said signal channel, the value of said second electrical impedance means being such as to insure the continued operation of its corresponding optical isolating circuit means in the event of a component failure in any of the other signal channels connected to said input circuit means.