| 摘要 |
PURPOSE:To enable a DC control signal to be sent in both directions, by providing one of a couple of information lines with a loop means capable of detecting a current direction, and the other with means of supplying electric power to the information lines and of changing supply potential directions optionally. CONSTITUTION:When a relay AA on a side A operates, a relay AB operates to form a loop for noninversion operation, and a current flows through the information lines to operates a loop detection relay BA on a side B, thus making a connection. When the side B answers, a relay D operates to invert a power potential, and a current flows through an inverting loop circuit on the side A to operate a relay E. Through the operation of the relay E, an answer memory relay EA operates and holds itself in operation. When the loop is broken during inversion once for a start signal for AC signal transfer and twice for an answer signal, the relay BA is released by breaking a contact SO, and the start signal is sent to a receiver-connection controlling circuit through relays BB, BG, BC, and BS. When a receiver is connected to the information lines, the relay D is released twice successively on the side B to hold the power potential of the information lines uninverted, thereby sending the answer signal. |
