| 摘要 |
PURPOSE:To enable to transmit and receive information other than a dial numeral by using a DTMF (push-button dial) signal of eight kinds of low group frequencies and seven kinds of high group frequencies as a pulsing signal. CONSTITUTION:When a subscriber's telephone set 1, which has the DTHF signal generation circuit of 56 kinds of the DTMF signals, i.e., the combination of 8 kinds of the low group frequencies and seven kinds of the high group frequencies, originates a call, the central control circuit 4 of an exchange controls a switch circuit 2 and connects the subscriber's telephone set 1 to a register circuit 3 with a DTMF signal reception identification circuit, and receives the DTMF signal from the telephone set 1. Besides, the central control circuit 4 identifies the received DTMF signal, and when it connects it to other exchange, it starts a sender circuit 5, and sends the DTMF signal to other exchange from the sender circuit 5.
|
