Dual tone decoding


Posted on Sep 8, 2012

Two integrated tone decoders, XR-567 units, can be connected (as shown in Fig. 1A) to permit decoding of simultaneous or sequential tones. Both units must be on before an output is given. R1C1 and R'IC'l are chosen, respectively, for Tones 1 and 2. If sequential tones (1 followed by 2) are to be decoded, then C3 is made very large to delay turn-off of Unit 1 until Unit 2 has turned on and the NOR gate is activated. Note that the wrong sequence (2 followed by 1) will not provide an output since Unit 2 will turn off before Unit 1 comes on. Figure IB shows a circuit variation which eliminates the NOR gate. The output is taken from Unit 2, but the Unit 2 output stage is biased off by R2 and CR1 until activated by Tone 1. A further variation is given in Fig. IC.


Dual tone decoding
Click here to download the full size of the above Circuit.

Here, Unit 2 is turned on by the Unit 1 output when Tone 1 appears, reducing the standby power to half. Thus, when Unit 2 is on, Tone 1 is or was present. If Tone 2 is now present, Unit 2 comes on also and an output is given. Since a transient output pulse may appear at Unit 1 turn-on, even if Tone 2 is not present, the load must be slow in response to avoid a false output due to Tone 1 alone. The XR-267 Dual Tone Decoder can replace two integrated tone decoders in this application.




Leave Comment

characters left:

Related Circuits

  • New Circuits

    .

     


    Popular Circuits

    Advanced Light Dimmer
    Hall-Sensor Current Monitor
    Subwoofer Filter Circuit Using Op-Amp TL072
    ac Validate Triac circuit
    amplifier Amp measures board twist (unfortunately!)
    Extensible Multiple Device Programmer 4 Base
    Home security alarm system circuit diagram
    Band Pass Filters
    early GEC transistor radio
    Capacitive load drive circuit diagram of the MAX4450 4451
    Super lock circuit diagram
    Based video surveillance system image sensor interface circuit
    Before power is in the hold state holding brake one circuit



    Top