| 摘要 |
PURPOSE:To miniaturize a circuit by constituting a switching circuit to switch the connection of telephone or facsimile with semiconductor elements. CONSTITUTION:In case of automatic dialing, an FET216 is made off, and a transistor (TR)210 is turned on during approximately 300ms, in such a period, the polarity inversion is detected by a photocoupler 208 to search the arrival of signal so that collision is prevented. If the polarity inversion is detected, a call signal is transferred from the net by which the TR210 is turned off but the FET216 is on. Also, the FET216 is turned off after the signal-arrival is detected by an arrival detecting mean 222, while a TR213 and an analogue switch 218 are turned on, and accordingly a D.C. circuit is formed. At the same time, an A.C. signal is lead to a facsimile main body 212. The operation of switching to automatic receiving from the waiting status is performed completely likewise. On the other hand, if the polarity inversion is not detected, a dial-form pulse is transmitted to the network by ON/OFF controlling the TR213.
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