| 摘要 |
<p>R. Treiber -1 SUBSCRIBER LINE TRUNK/CIRCUIT A microprocessor controlled subscriber line circuit for interfacing analog telephone lines and trunks to a digital switching system is disclosed. All processing of incoming analog signals is accomplished by the line circuit, including the interface between the line and a digital switching matrix, measuring, monitoring, testing of the signals associated with the speech path, generating talking battery, ringing and other tones, equalization and providing the two-wire to four-wire conversion with acceptable echo performance and minimized cross-office transmission loss. The analog-to-digital and digital-to-analog conversions are accomplished under microprocessor control as are the tone and power generation functions in a programmable power supply configuration utilizing pulse duration modulated feedback control in a programmable signal generator. The described subscriber circuit is particularly advantageousin that it is designed to maximize its implementation using solid state circuit techniques and LSI devices as opposed to conventional audio components and relays.</p> |
