TREE

The modem off indicator is intended especially for serious Internet surfers. It will be seen that the circuit of the indicator cannot be much simpler, or there might be nothing left. In spite of its simplicity, it may prove to be a cost-saving device, since it shows at a glance whether the telephone line is free again after the modem has been used. This obviates high telephone charges in case for some reason the modem continues to operate. The circuit depends on the fact that there is a potential of about 40 V on the telephone line when it is not busy. This voltage drops sharply when a telephone call is being made. If, therefore, the circuit is linked to telephone terminals a and b, the lighting of the green LED shows that the line is not busy in error. Circuit diagram: Modem Off Indicator Circuit Diagram The bridge rectifier ensures that the polarity of the line voltage is of no consequence. This has the additional benefit that polarity protection for the LED is not necessary. To mak...

This simple ON OFF touch switch circuit is based on the well known timer IC 555 (IC1), which drives a relay that acts like a switch. The metal surfaces can have what form we want, but it should be clean and very close to the circuit. Read more  WC fan using 555 Touch plate MP1 in order to close the contact of relay RL1 [ON], or plate MP2 in order to open the contact of RL1 [OFF]. The Led D2 turns on when the contacts of RL1 are closed. Two small pieces of metal can be used as sensor plates. 555 ON/OFF Touch Switch Schematic     Parts List R1 = R2 = 3.3M R3 = 10K R4 = 1K C1 = 10nF D1 = 1N4007 Q1 = BC547 IC = NE555 12V relay Sourced By: Circuitsstream

Per request the circuit today we have relay circuit. It is worth noting again that the diagram provides a time delay of about 0.5 seconds for every microfarad in the value of capacitor C1. This permits delays of up to several minutes. If desired, the delay periods can be made variable by replacing resistor R2 with a fixed and variable resistor in series whose nominal values are approximately equal of the total value of R2 (680K). Automatic Turn Off Relay Circuit Diagram

The modem off indicator is intended especially for serious Internet surfers. It will be seen that the circuit of the indicator cannot be much simpler, or there might be nothing left. In spite of its simplicity, it may prove to be a cost-saving device, since it shows at a glance whether the telephone line is free again after the modem has been used. This obviates high telephone charges in case for some reason the modem continues to operate. The circuit depends on the fact that there is a potential of about 40 V on the telephone line when it is not busy. This voltage drops sharply when a telephone call is being made. If, therefore, the circuit is linked to telephone terminals a and b, the lighting of the green LED shows that the line is not busy in error. The bridge rectifier ensures that the polarity of the line voltage is of no consequence. This has the additional benefit that polarity protection for the LED is not necessary. To make sure that the telephone line is not loaded unnecessa...

 Modem Off Indicator Circuit Diagram . The modem off indicator is intended especially for serious Internet surfers. It will be seen that the circuit of the indicator cannot be much simpler, or there might be nothing left. In spite of its simplicity, it may prove to be a cost-saving device, since it shows at a glance whether the telephone line is free again after the modem has been used. This obviates high telephone charges in case for some reason the modem continues to operate. The circuit depends on the fact that there is a potential of about 40 V on the telephone line when it is not busy. This voltage drops sharply when a telephone call is being made. If, therefore, the circuit is linked to telephone terminals a and b, the lighting of the green LED shows that the line is not busy in error.  Modem Off Indicator Circuit Diagram The bridge rectifier ensures that the polarity of the line voltage is of no consequence. This has the additional benefit that polarity protection for t...