Two port signalling voltages filter arrangement
AssigneeBritish Telecommunications public limited company
InventorJohn W. Cook
Life of this patent
Estimating the term…
Abstract
A twisted-pair telephone line is connected to a conventional telephone via a low-pass filter and equipment for receiving signals in an upper frequency range, e.g., 25-1000 kHz via a high-pass filter. The low-pass filter is primarily passive (to allow passage of line power, ringing and signalling voltages) but, to improve matching to non-resistive line and telephone impedances, at least the main part of the filter is flanked by impedance convertors in which amplifiers having an appropriate transfer function feed voltages back into the line via transformers through which power, ringing and dialing may pass unimpeded.
Claims8
A telecommunications station comprising:
- a line port connected to a transmission line having a frequency dependent characteristic impedance;
- a high-pass filter connected between the line port and means for transmitting and/or receiving signals in an upper frequency band;
- a low-pass filter arrangement connected between the line port and telephony apparatus for communication in a lower frequency band;
- wherein the low-pass filter arrangement comprises a passive filter and an impedance conversion arrangement having two ports connected respectively to the passive filter and to the transmission line;
- the impedance conversion arrangement comprising a conductive path between the two ports so as to be substantially transparent to d.c. and to pulse and ringing components exceeding a predetermined amplitude, and an amplifier connected to receive signals from the conductive path and to deliver to the conductive path a current or a voltage that is a frequency-dependent function of the received signals.
A filter for connection to a source or load having a frequency-dependent impedance, comprising a passive filter and an impedance conversion arrangement having two ports of which one is connected to the filter and the other is for connection to a source or load;
- the impedance conversion arrangement comprising a conductive path between the two ports so as to be substantially transparent to d.c. and to pulse and ringing components exceeding a predetermined amplitude, and an amplifier connected to receive signals from the conductive path and to deliver to the conductive path a current or a voltage that is a frequency-dependent function of the received signals.
Dependencies are inferred from the claim text.