| 摘要 |
PURPOSE:To make it possible to enter for data communicaion comparatively easily even if an expensive data exchange is not installed, by providing two timing citcuits in the line start detecting circuit of the subscriber's circuit connected to the exchange. CONSTITUTION:Two timing circuits are provided in the line start detecting circuit of the subscriber's circuit connected to telephone exchange SW, and line start is detected by completion of closure of the loop of the line within the second timing T2 after the first timing T1. For example, when the data communication terminal unit closes instantaneously the loop for originating, it is detected by the photo coupler light emission-side element, and the light receiving side is turned on, and charge of capacitor C is discharged through resistance R1, and monostable multivibrator MMO is started at point (b) after timing T1 and issues the output during timing T2. If closure of the loop is completed within timing T2, photo coupler PT is turned off, and monostable multivibrator MM1 is started through the NAND element at point (c), and line relay DL for data communication subscriber is operated. |
