| 摘要 |
The invention relates to a device for securing a telephone line (1) between a terminal (10) and a telephone exchange (2). According to the invention, said securement device (30, 40) comprises the following: a transmitting circuit (30) of the telephone line (1), at the terminal end (10), said circuit transmitting a securement signal (S(t)) that is modulated by a carrier wave (A(t)) to a chosen frequency (f) in the audible range; and a control module (40), which is connected to the telephone exchange (2) and which comprises a transmission line (41), a processing circuit (42), said processing circuit being parallel on the transmission line (41) and being suitable for demodulating the securement signal (S(t)) and for generating an estimated signal (Ŝ(t)) of the securement signal, and a subtractor circuit (43) that is placed on the transmission line (41) at the output of said processing circuit (42). The inventive device can be used in public or private telephony. |
