The well-known ‘sleep’ function in clock radios and television sets switches off the equipment after a preselected time. However, what good does it do to put the television into standby mode while the stereo set or DVD player that is connected to it remains unaffected? The sleep timer described here sends standby codes to several RC5-compatible devices at the same time.Function and operationThe circuit shown in Figure 1 allows you to select the equipment that will be switched on or off as well as the sleep time, which might better be called the delay time. The sleep timer is operated using four pushbutton switches. The current state of the timer is indicated by four LEDs, each of which corresponds to 30 minutes of time delay. In normal operation, these diodes are enabled for only one second out of every ten, in order to save energy.