| 摘要 |
PURPOSE:To attain the attenuation equivalent to a case where a digital signal is attenuated by an analog signal without using a D/A converter nor an A/D converter, by using a memory which uses an input digital signal directly as an address signal. CONSTITUTION:A digital signal A of an 8-bit compressed PCM signal, etc., a control signal D for conversion of attenuation factor, a switch signal E of a PCM compression system, etc. are supplied to a memory 5 as address signals. The memory 5 is divided into data areas of mu-los and A-low systems respectively with the signal E used as a highest digit address. These two areas are divided further into areas corresponding to each attenuation factor with the signal D used as the address of the next digit. In other words, the 8-bit compressed PCM signal is converted into a 12-bit or 13-bit linear code according to a PCM compression system and multiplied by 10<-x/20> times (x: attenuation factor dB). This linear code is converted again into the 8-bit compressed PCM signal by the PCM compression system and stored to each address as data. Then the data corresponding to each stored address is delivered F after the address signals of each digit are supplied. |
