| 摘要 |
An apparatus for generating tone signals in the terminal equipment of a digital telecommunication system, the form of the signals being determined by digital condition information obtained from the exchange, e.g. a ringing tone signal or busy tone. The apparatus includes a memory (4) with a number of memory fields, the binary content of which represents discrete values in a tone frequency signal between two zero passages. The counter positions in a counter (5) are each associated with a memory field such that the periodical activation of the positions after each other provides a read-out to a D/A converter of the memory field associated with the respective position. A control circuit (9, 10) modulates the signal obtained from the periodical read-out in time with a condition signal determined by the condition information obtained from the exchange. The control circuit is activated when the counter is set to zero such that the beginning and end of the modulation coincide with the zero passages of the tone frequency signal. |
