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目前,不少按键式电话具有音乐保持功能,当通话的一方因故需让对方暂候片刻时,按下“HOLD”键(保持键),机内便可传出悦耳的音乐,消除了主叫方等待的烦恼;而当被叫方摘机又可即时通话。 音乐保持功能是如何产生的呢?下面以HA988(Ⅳ)P/TSD型话机电路为例加以说明。许多电话的这类电路与它大同小异,因此,掌握了其原理,对其它话机音乐保持电路便可自行分析了。
At present, many push-button phones have a music-holding function. When one of the parties for the call needs to wait for a moment for some reason, pressing the “HOLD” key (hold button) causes the melody to be heard in the machine, eliminating the main Called the party waiting for trouble; and when the called party pick up the phone again immediately. How is the music hold function produced? The following uses the HA988 (IV) P / TSD telephone circuit as an example. Many of these types of circuits are similar in nature to their circuits, and therefore, have mastered their principles and are self-analyzing for other phone music holding circuits.