Phone Busy Indicator
Have you ever been using the modem or fax and someone else picks up the phone, breaking the connection? Well, this simple circuit should put an end to that. It signals that the phone is in use by lighting a red LED. When the phone is not in use, a green LED is lit. It needs no external power and can be connected anywhere on the phone line, even mounted inside the phone. Note: This circuit may cause problems for some when used. You may want to build a different circuit. Schematic Parts: Part Total Qty. Description Substitutions R1 1 3.3K 1/4 W Resistor R2 1 33K 1/4 W Resistor R3 1 56K 1/4 W Resistor R4 1 22K 1/4 W Resistor R5 1 4.7K 1/4 W Resistor Q1, Q2 2 2N3392 NPN Transistor BR1 1 1.5 Amp 250 PIV Bridge Rectifier LED1 1 Red LED LED2 1 Green LED MISC 1 Wire, Case, Phone Cord Notes: 1. This is a very simple circuit and is easily made on a perf board and mounted inside the phone. 2. LED1 and...