| 摘要 |
PURPOSE:To add a special function efficiently by allowing the talk circuit of a telephone set to be switch and connected to a leased line and a speech line from a main device, and applying a common function circuit to both the leased line and speech line. CONSTITUTION:The speech line Lt1 is connected to line terminals a1 and b1 of the telephone set, a trunk line Lp2 is connected to line terminals a2 and b2, and a signal line Ls1 is connected to terminals d1 and d2. The speech line Lt1 and the trunk line Lp2 passed through a loop monitoring circuit LPS are connected to a talk circuit TKC through contacts lr<0> and lr<1> of a changeover relay LR and a diode bridge DB1 and a pulse sending circuit DSP for dial oscillation. A main control part CNTM has internal memory and controls respective relays and the function circuit according to states of respective switches on a keyboard KB and a hook switch Hs<2>. A circuit LPS holds the trunk line Lp2. Thus, the special function is added effectively to both the speech line to both the main device and the leased line. |
