Starfire Zhu wrote:
>
> Hi, there!
>
> Greetings to those who noticed this message.
>
> Could you tell me the simplest way to control the AC signal? I mean I
> want to switch the signal on or off with a I/O pin form my PIC. The
> signal is kind of voice or low frequency. By the way, a solution with a
> relay is not expected, there must be other ways....
>
> Can anyone shed  a light to me?
>
> Thanks in advance!

  Knowing the voltage of the signal would help here (If it's reasonably
low voltage, an analog switch or the like would be a decent way to go.)
For example see the 74HC4016.  (Knowing more about the spceifics always
helps us help with a circuit.)

  I'm assuming your signal's under 50kHz or so from what you say <G>
Analog switches do have bandwidth limitations, and voltage range limits,
but pass voice & slow video without problems...  As always, read the
spec sheet, and as always, finding the right spec sheet to read is part
of the problem!  Some analog switches need bipolar supplies for AC
voltages (you could, with a 4016, capacitively couple input & output to
solve this, loosely dc biasing the Switch sides of the capacitors to
center them at Vcc/2, though.)

  I've used a logic-controlled Analog switch that controls pure AC
signals but it's late & I don't remember the part number tonight.
Anyone?

  Mark, mwillis@nwlink.com