Telephone answering device for PBX - has switching means responding to control signal from calling extension

摘要: The control signal or combination consists of low frequencies in the PBX transmission band. transmitted by calling extension is produced a whistle and converted its microphone into an electric signal; generated electro-acoustical generator, a.f. generator delivered directly to exchange line; lies outside telephone frequency device enables user leave information for expected unexpected caller from another when he will be absent, thus making further call unnecessary.