In order to improve the ringing method of telephone used in power systems, a type of selective calling device using audio frequency has been developed.
为了使电力系统通信设备的呼叫装置更加使用方便工作可靠，我们研制了以按键电话机发出双音频呼叫信号进行选择接收的音频选号装置。
In order to improve the ringing method of telephone used in power systems, a type of selective calling device using audio frequency has been developed.
为了使电力系统通信设备的呼叫装置更加使用方便工作可靠，我们研制了以按键电话机发出双音频呼叫信号进行选择接收的音频选号装置。
应用推荐