| 摘要 |
PURPOSE:To reduce errors in recognition due to nose generated when a reception-side switching device changes connection without prolonging the reception time of a multifrequency signal by providing a receiving circuit with a special signal confirmation signal generating circuit and a comparing circuit. CONSTITUTION:An originating exchange 13 and a terminating exchange 22 which connect an automatic switching network to a repeating exchange through trunk lines 4 and 5 are connected, and an outgoing sensor OS15 which has a confirmation signal receiving circuit is connected to this exchange 1. The frequency discriminating circuit 152 of this confirmation signal receiving circuit discriminates a special confirmation signal sent back from an exchange 3 through specific processing and an error detecting circuit 153 detects whether the number of errors as the result of the discrimination result shows two frequencies or not and inputs the detection result to an output determining circuit 154. This circuit 154 determines a signal present signal and a special confirmation signal, which are outputted to terminals 155 and 156 and also applied to a comparing circuit 157. Then, the circuit 157 compares them with the special confirmation signal from a special confirmation signal generating circuit 158 and applies a switching signal to the circuit 154 when the comparison result shows coincidence, thereby preventing an error in recognition originating from a change in connection. |
