Patent ID: 6891947

Claim:
A multifunctional analog trunk (TRK) circuit provided in a switching system connected with a central office line, said TRK circuit being connectable between (1) a tip terminal, “M” terminal and “E” terminal of said switching system and (2) a hybrid circuit and codec of a switching circuit, said TRK circuit comprising: a first relay connectable with said tip terminal of said switching system; a second relay for connectable with a ring terminal of said switching system; said first relay and said second relay provide control of a polarity reverse in DID (Direct Inward Dialing tie line) trunk mode; a transformer comprising a primary coil and a secondary coil, an upper end of said secondary coil connectable with the codec and hybrid circuits of said switching circuit and a lower end of said secondary coil is grounded; a third relay connected between an output of said first relay and an upper end of the primary coil of said transformer for occupying a loop in one of a loop and a ground start TRK mode; a ring path connected in parallel with both ends of said third relay for transfering a ring signal coming from said central office line; a fourth relay driven in said ground start TRK mode, said fourth relay being cut off when said third relay occupies said loop; a tip ground detection circuit connected with an output of said fourth relay for detecting a grounding of said tip terminal in said ground start TRK mode; a fifth relay connected with an output of said second relay to be driven in said ground start TRK mode; a ring ground enable circuit connected with an output of said fifth relay for grounding said ring terminal in said ground start TRK mode; a bridge diode connected in parallel with the primary coil of said transformer for full-wave rectification of a signal transferred through said ring path; a sixth relay connected between said ring path and said bridge diode; a seventh relay connected between said bridge diode and the output of said second relay; said sixth relay and said seventh relay for providing dial pulses in said loop or ground start TRK mode; a bypass circuit connected with an output of said bridge diode to bypass a direct current voltage output of said bridge diode in said loop or ground start TRK mode; a ring and HOS detection circuit connected with said bypass circuit for detecting the ring and HOS signal in said loop or ground start TRK mode, and said HOS signal in said DID TRK mode; a feeding circuit connected with said “M” terminal to supply a prescribed source voltage to said sixth and seventh relays; an eighth relay connected with said “M” terminal for grounding said “M” terminal when idle and for supplying said source voltage to said “M” terminal in E&M TRK mode; and, an HOS signal detection circuit connected with said “E” terminal to detect said HOS signal in said E&M TRK mode.