Distance alarm circuit

Discussion in 'The Projects Forum' started by jr1964, Mar 17, 2009.

  1. jr1964

    Thread Starter New Member

    Mar 17, 2009
    I'll describe what I'm looking for since I'm not sure what the correct name would be, or if it even exists:

    a) I have a static base
    b) I have a portable transmitter
    c) When (a) is more than xxx feet from (b), an alarm will sound.

    Both components should be small and portable and the effective distance should not be more that 30~50 yards.

    Any ideas?