Signal transmission devices
First Claim
1. A signal transmission device comprising a signal path extending between respective terminals of an input and an output port of the device, a controllable, substantially load independent current source shunting said signal path at a point intermediate said input and output ports, impedance means connected in each series circuit including the terminals of a respective port of the device and the shunt path provided by said current source for presenting at each port an impedance which is high in relation to that of a signal source to be coupled to said input port or of a signal load to be coupled to said output port, as the case may be, said current source being responsive to a voltage signal applied at the terminals of said input port to provide a corresponding magnitude of output current, and means being provided for determining the relative proportions of the current from said current source which pass through the respective impedance means in the input and output circuits of the device, thereby to determine the virtual impedances of the device presented at said input and output ports respectively and to determine the signal gain provided by said device.
3 Assignments
0 Petitions
Accused Products
Abstract
A signal transmission device capable, for example, of use as a hybrid circuit in a voice frequency telephone transmission system, comprises a controllable substantially load independent current source shunting a signal path between input and output ports of the device. The shunt path is de-coupled from a signal source or load to be connected to respective ports of the transmission device by series connected impedances which are high in relation to those of the respective source or load, while the current source is arranged to respond to a voltage signal applied to the input port in order to drive corresponding currents through the impedances. A current steering circuit is provided to determine the relative magnitudes of the currents driven through the respective impedances, and thus to determine the virtual impedances presented to the signal source and load as well as the signal gain of the device.
20 Citations
7 Claims
- 1. A signal transmission device comprising a signal path extending between respective terminals of an input and an output port of the device, a controllable, substantially load independent current source shunting said signal path at a point intermediate said input and output ports, impedance means connected in each series circuit including the terminals of a respective port of the device and the shunt path provided by said current source for presenting at each port an impedance which is high in relation to that of a signal source to be coupled to said input port or of a signal load to be coupled to said output port, as the case may be, said current source being responsive to a voltage signal applied at the terminals of said input port to provide a corresponding magnitude of output current, and means being provided for determining the relative proportions of the current from said current source which pass through the respective impedance means in the input and output circuits of the device, thereby to determine the virtual impedances of the device presented at said input and output ports respectively and to determine the signal gain provided by said device.
Specification