Abstract: A digital communication system comprising a host and a client, the host calls the client via two transmission lines. The host includes a processor, a first control unit, a second control unit, a high frequency transformer and an interface unit. The digital communication system utilizes the first control unit and the high frequency transformer to modulate outgoing signals. The digital communication system utilizes the second unit and the high frequency transformer to demodulate incoming signals.

Abstract: A digital communication system comprising a host and a client, the host calls the client via two transmission lines. The host includes a processor, a first control unit, a second control unit, a high frequency transformer and an interface unit. The digital communication system utilizes the first control unit and the high frequency transformer to modulate outgoing signals. The digital communication system utilizes the second unit and the high frequency transformer to demodulate incoming signals.

Abstract: A portable electronic device includes a plurality of touch sensing units for covering a surface of the portable electronic device. Each touch sensing unit is capable of generating touch sensing signals when the touch sensing units are touched. The portable electronic device stores at least one predetermined figure. The portable electronic device determines positions of the touched touch sensing units on the surface of the portable electronic device when the touch sensing unit is touched, and generates a touch figure according to the determined position of each touched touch sensing unit on the surface of the portable electronic device. The portable electronic device computes a similarity degree between the generated touch figure and the predetermined figure, and generates an alarm instruction to control an alarm unit to output an alarm signal if the computed similarity degree is greater than the predetermined value.