| 摘要 |
A technique for powering telephone lines using an unbalance current source and current sink (100), and a technique for improving attenuation/frequency distribution and return loss (impedance matching) of transformer-coupled wire-line communications circuits by using secondary series capacitance and an AC current pump signal source (106), and a generation of ringing voltage (400) as positive voltage pulses with respect to a negative power supply voltage; and a technique for removal of AC power ripple by using an active linear floating filter for the purpose of powering telephone line circuits, and a technique for injection of real time tone samples into T1 transmissions circuits by use of a T1 framer idle code register (504). The combination of the above five circuit techniques provides for the hardware implementation of a single printed circuit board embodiment (Line Interface Unit LIU) of a plurality of communications functions including a T1 channel service unit, a ringing generator (400), power converters, a ringback tone generator, and a channel bank controller. The LIU (1020) supports selectable T1 standards of communications. Dual 12-channel telephone line voice cards plug into the LIU card (1020) to provide a complete T1 channel bank control process and apparatus (501). The invention solves telephone line interface, power filtering, ringing generation, and tone injection problems with lower component complexity, costs, and physical size than prior art solutions.
|
