| 摘要 |
PURPOSE:To prevent an amplifier constituting a carrier from being appllied with an overload even if a connection confirmation signal for a switchboard (dial tone, busy tone, etc.) more than a prescribed value is inputted, by providing an amplitude adjusting circuit to the carrier. CONSTITUTION:Except during a calling time, input 1 is grounded and input 3 is in an open state. In consequence, AND gate 3 is closed, whose output makes switch circuit 1 open. The output of inverter 4, on the other hand, allows switch circuit 2 to conduct and a connection confirmation signal of more than the prescribed value from input 2 is passed through switch circuit 2 and adjusted by level adjusting circuit 5 to the prescribed level of the carrier before being sent out to the output by way of OR gate 6 and amplifier circuit 7. In the calling state, inputs 1 and 3 are both grounded and a sound talking signal from input 2 is outputted by way of switch circuit 1, OR gate 6 and amplifier circuit 7. |
