Electronics and Telecommunications Research Institute

Korea Telecommunication Authority

Kwang Uk Chu

In Ho Hwang

Yong Hyub Won

Ki Hwan Kim

Jong Kyu Kim

Dae Heon Lee

Byeong Hoon Kim

Sang Woo Cho

Seo Y Shin

An apparatus for preventing leakage of a weak signal from a speaker is provided. The apparatus passes a normal speaker drive signal coming through speaker signal lines and blocks a weak signal generated by the sounds around the speaker, thereby preventing wiretapping the speaker.

Apparatus for preventing leakage of a weak signal from a speaker

Provided is a device for preventing eavesdropping through a speaker. More particularly, a device for preventing eavesdropping by transmitting a jamming signal through a speaker common signal line is provided, the device including: a jamming signal generator for generating a jamming signal comprising a noise signal; an amplifier for amplifying the jamming signal; and a transformer for receiving the amplified jamming signal from the amplifier and outputting the amplified jamming signal to a speaker common signal line. The device may transmit a jamming signal in an audible frequency band to the speaker common signal line, thereby rendering conversations unrecognizable to eavesdroppers when an electrical signal induced from a speaker is detected through the speaker common signal line.

Device for preventing eavesdropping through speaker

An optical exchanging apparatus is disclosed including N optical transmitters for generating optical signals each having a single constant mode, N mode converters for converting modes of the optical signals generated from the optical transmitters according to a mode-converting signal, an Nx1 coupler for coupling the mode-converted optical signals generated from the mode converters to be supplied to one terminal, a 1xN distributor or distributing the coupled optical signal generated from the Nx1 coupler to N optical signals each having various modes, N mode selectors for respectively passing only the optical signal of a selected mode out of the N optical signals generated from the 1xN distributor, and N optical receivers for receiving the optical signals generated from the mode selectors.

Optical exchanging apparatus using mode conversion and mode selection in

A simultaneous optical compression and decompression apparatus having a simple symmetrical arrangement including a plurality of optical splitting/combining units capable of achieving simultaneous splitting and combining of optical signals in opposite directions, a plurality of optical delay units each arranged between adjacent ones of the optical splitting/combining units and adapted to delay the time taken for an optical signal to pass therethrough in each of opposite directions by a predetermined time, so as to reproduce the optical signal in accordance with a predetermined rule. The apparatus also includes a pair of optical isolation units respectively connected to opposite end-side ones of the optical splitting/combining units, each of the optical isolation units being adapted to allow an optical signal to pass therethrough in one direction; a pair of optical switching units respectively connected to opposite end-side ones of the optical splitting/combining units and adapted to switch optical signals output from the optical splitting/combining units in response to control signals, so as to allow predetermined optical signals to pass therethrough; and a pair of control units respectively connected to the optical switching units and adapted to apply the control signals to the optical switching units.

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Daejeon, South Korea

Kwang Uk Chu