A switching network has a group of incoming lines respectively connected to the terminal equipments of a plurality of subscriber stations. A group of outgoing lines are respectively connected to a plurality of trunk circuits. A plurality of crosspoints are formed between the incoming lines and the outgoing lines. Crosstalk is eliminated between mutually adjacent incoming lines or between mutually adjacent outgoing lines, by serially connecting a series circuit between the lines where crosstalk might otherwise occur. The serial circuit includes a phase inverter circuit and an impedance element having an impedance value which is sufficiently close to that of the impedance which is likely to cause crosstalk between these lines.
4697047 - Trunk coupling unit - Owned by Hitachi, Ltd. (Tokyo,JP) Hitachi Computer Engineering Co., Ltd. (Kanagawa,JP)
A relay circuit comprise first and second relays having respective terminals at which positive cross-talk of a signal of positive polarity is produced when the other terminals to which the positive polarity signal is applied are in the make and break states, respectively, and third and fourth relays having respective terminals at which negative cross-talk of a signal of negative polarity is produced when the other terminals to which the negative polarity signal is applied are in the make and break states, respectively, wherein with regards to the terminals where the cross-talk occurs, the first and fourth relays are connected to each other and said second and third relays are connected to each other, respectively.
A device for reducing or eliminating differential mode cross-talk between data communication channels (CH1 and CH2) in a balanced communication system by coupling one or more auxiliary capacitances (C100) across the transmission lines (A, A, B, and B) between the two channels (CH1 and CH2), thereby augmenting the intrinsic capacitive couplings (CA.sub.AB, C.sub.AB, C.sub.BA, and C.sub.BA) and leakage between the channels in order to net the differential cross talk signal to zero.
A crosstalk noise calculation method for calculating crosstalk noise among a plurality of wirings, includes calculating a crosstalk noise using a function in which the crosstalk noise becomes approximately constant when a predetermined wiring length is exceeded, so as to improve the design efficiency of the wirings by preventing an excessively strict checking from being performed.
The eavesdropping prevention system and method of the present invention provides for shunting leakage signals in a communication system. The amplifier-based coupler is constructed with amplifiers configured with a nearly-zero impedance path which effectively prevents the propagation of a leakage signal onto other communication connections which are coupled to the same communication device. Leakage signals are attenuated due to the nearly-zero impedance path, rather than propagating through the higher impedance communication connections.
