| 摘要 |
PURPOSE:To improve privacy telephone performance and to simplify the re-setting of a privacy telephone key by performing the re-setting of a new privacy telephone key generated from a privacy telephone key generation circuit on a master device with a slave device by using an optical signal. CONSTITUTION:When the change of the privacy telephone key is instructed with the key input part 13 of the slave device 40 by an operator, the privacy key generation circuit 12 generates an appropriate privacy telephone key, for example, by generating a random number, etc., and it is registered on a memory circuit 11, The new privacy telephone key is inputted to a privacy telephone circuit 7, and following making of a telephone into the privacy telephone and decoding are performed with the privacy telephone circuit 7, and also, it is transmitted to the light reception circuit 5 of the master device 30 with a light transmission circuit 10 as the optical signal L. The master device 30 stores the privacy telephone key in a memory circuit 4, and following communication with the slave device 40 by radio W is made into the privacy telephone and decoded with a privacy telephone circuit 2. Even when a third party nearby is provided with the similar telephone system, no influence on the master device of the third party is applied since light is shielded, which prevents tapping performed. |
