Speaking Doorbell: SpeDoB was designed and built to gain experience with the PIC microcontroller. This doorbell uses a speech recorder integrated circuit (ISD series) to play back3 pre-recorded "theres someone knocking on the door" messages. Its a very easy and simple project to build, ideal for beginners!
Timed Beeper: Beeps 7.5 seconds after a preset Time Adjustable Time settings:15 sec.30 sec.1 min.2 min. & others
Two Tone Generator: This two-tone generator includes 3 ICs - NE555 Astable Multivibrators. You can vary the duration of each tone by changing the 10k resistor or 100MF capacitor at IC1 or changing resistors and capacitors at IC1/2 for higher or lower tone.
You've got Mail: 08/19/99 EDN-Design Ideas / Many e-mail programs provide a "beep" or a pop-up message box signaling the user that a new e-mail message has arrived. If you are too far from the computer to hear the audible signal or if the monitor is turned off, then you miss the new-mail audible and visual signals. The simple circuit in Figure1 latches on an LED and an audio sounder when an appropriate new audible e-mail signal occurs. The method replaces the normal e-mail sound.wave file with a .wav file of any valid recorded dual-tone multifrequency (DTMF) sound.