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Is there a dual NE567?

Discussion in 'Electronic Design' started by [email protected], Mar 20, 2008.

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  1. Guest

    I'm currently designing a circuit with two NE567's(tone decoder PLL)
    in it, so I'm wondering if there is an IC which contains two tone

    Thanks in advance

    Ferdinand Meyer-Hermann
  2. John Fields

    John Fields Guest

  3. Guest

    The circuit is an intercom over a 2-wire interface. The goal is to be
    able to use many stations on the same two wires and call them. My idea
    was to superimpose an ultrasonic tone on the speech signal to do that.
    So one NE567 is used to decode the tone and the other is used to make
    it (a NE567 is a nice sawtooth oscillator with only two external
    components). I could also use a 555 for this purpose, but combining
    two NE567 would save a chip and an extra 555 would never save one.
    I haven't found any, but I could email the schematic to you. Maybe you
    find the perfect solution...?

  4. John Fields

    John Fields Guest

    Maybe. ;)

    In keeping with the spirit of the newsgroup, though, it would be
    better if you posted it somewhere where we can all access it. Since
    you can't access any of the binary USENET groups through Google that
    rules out alt.binaries.schematics.electronic, but maybe you can post
    it to a website somewhere and then post the URL here?
  5. MooseFET

    MooseFET Guest

    I'm going to be the first in this thread with a "use a PIC" solution:

    The PIC can read some dip-switches to know its station number. The
    ADC can sample the signal from the two wires and code can look for
    this stations frequency. The call signal can be a tone made by
    wiggling a port output.

    Now for a non-PIC based idea:

    The LTC6906 makes a squarewave output with just a single resistor.
    Changing the resistor value makes different frequencies for selecting
    which station to call. The part is about as small as the capacitor
    you'd need with any other sort of oscillator.

    The decoding could be done by making basically a superhet radio. An
    oscillator can be set just a small amount off the frequency for the
    call signal and then a simple mixer could turn the call signal into a
    tone in the audio band that is sent to the speaker to alert the user.
  6. Guest

    This could be a solution kicking a bunch of electronics out of the
    device. But it requires some modifications. See below...
    I'd prefer the sawtooth generated by the NE567, because it has a lower
    harmonic content. But, if I find a source of these, I'll consider
    Note that this is a hobbyist's project, so I need to buy in small
    I think you misunderstood the design. The tone is intended to unmute
    the speaker, so that the real call can be done by voice. That's why
    the call tone needs to be ultrasonic.

    Here is the schematic (my webserver is down at the moment, so I had to
    use imageshack)

    Some explanations:
    The intercom is going to be used to link several flats spread over two
    houses. Because people (especially some old women) live there, the
    intercom needs to be as easy-to-use as possible, i.e. press button,
    speak, release button, await answer.

    You too can't expect these people wait for the line to become
    inactive, so an interlock is included to avoid collisions on the
    That's why the line is raised to 2V while speaking, allowing simple
    detection whether the line is in use or not.
    Sometimes there will be need to call everyone, so every station will
    react on a DC level on the line above 5V and unmute the speaker.
    There is also support for an entry-phone. Because one can't expect
    strangers to understand what a PTT is for, the PTT is moved into the
    other stations.
    The TAA4761 is a quad operational amplifier with high-current open-
    collector output.

    BTW: I'm from Germany so please be gentle with my English...

    Ferdinand Meyer-Hermann
  7. MooseFET

    MooseFET Guest

    Try They carry lots of linear stuff.

    Yes, perhaps I did. I had assumed that a person had to do something
    at the receiving station.
    Here is the schematic (my webserver is down at the moment, so I had
    to There is something wrong with the image. I can't see much of it.
    There is a big square blank in the middle.
    Are they talking to a central station?

    Your english is quite good.

    Perhaps more later. I've got to run.

  8. says that National has
    discontinued the LM567 but still makes the low power version, the
    LMC567. You should have no problem finding a vendor of National
    Semiconductor in Germany.

    -- is home to cowards and terrorists

    Add this line to your news proxy nfilter.dat file
    * drop Path:*!not-for-mail to drop all traffic.
  9. Guest

    No, there is no central station except a central 15-20V power supply.
    All stations are wired in parallel. So there needs to be sort of an
    algorithm to arbitrate who is will use the line next.

    I have no trouble getting the LM/NE/SE 567. The problem is the
    Ooops, I really don't know what has happened to the schematic, but
    here is another try:

    Happy Easter!
    Ferdinand Meyer-Hermann
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