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2 LINE TELEPHONE LINE STATUS INDICATOR
Many home businesses use multiple phone lines. This circuit gives you a visual indication when a line is in operation. The two AA battery cells should provide enough power for about one year of
operation. The circuit is line polarity insensitive.
2.45GHz RF Signal Detector
This passive RF indicator is made from a few simple parts. A 100uA moving coil meter is used to display the relative intensity of the RF signal. This circuit can be used with some
cell phones and many cordless telephones. (added 7/06)
4 LINE TELEPHONE LINE STATUS INDICATOR
Many home businesses use multiple phone lines. This circuit gives you a visual indication when a line is in operation. The two AA battery cells should provide enough power for about one year of
operation.
Links to electronic circuits, electronic schematics, designs for engineers, hobbyists,
students & inventors:
2 Line Intercom Plus a Telephone Changeover Switch: The circuit presented here can be used for connecting two telephones in
parallel and also as a2-line intercom. FAIR WARNING -- THIS SITE HAS ANNOYING POP UP ADS. (added 6/06)
5 Band Graphic Equalizer using a Single IC/Chip: This circuit uses a single chip, IC BA3812L for realizing a 5 band graphic
equalizer for use in hi-fi audio systems. The BA3812L is a five-point graphic equalizer that has all the required functions integrated onto one IC. The IC is comprised of the five tone control
circuits and input and output buffer Amplifiers. The BA3812L features low distortion, low noise, and wide dynamic range, and is an ideal choice for Hi-Fi stereo applications. It also has a
wide operating voltage range (3.5V to 16V), which means that it can be adapted for use with most types of stereo equipment.
The five center frequencies are independently set using external capacitors, and as the…. (added 6/06)
AN-347: Shielding and Guarding: AN-347 - Analog Devices Application Notes (app note added 6/06)How to Exclude
Interference-Type Noise. What to do and Why to do it-A Rational Approach
Audio Visual Indicator for Telephones: Many a times one needs an extra telephone ringer in an ad joining room to know if
there is an incoming call. For example, if the telephone is installed in the drawing room you may need an extra ringer in the bedroom. All that needs to be done is to connect the given circuit
in parallel with the existing telephone lines using twin flexible wires. This circuit does not require any external power source for its operation. The section comprising resistor R1 and
diodes D5 and LED1 provides a visual indication of the ring. Remaining part of the circuit is the audio ringer based on IC1 (BA8204 or ML8204).... (added 10/05)
Audio Visual Ringer: Many a times one needs an ex- tra telephone ringer in an ad- joining room to know if there is an
incoming call. For example, if the telephone is installed in the drawing room you may need an extra ringer in the bedroom. All that needs to be done is to connect the given circuit in parallel
with the existing telephone lines using twin flexible wires. This circuit does not require any external power source for its operation. The section comprising resistor R1 and diodes D5 and
LED1 provides a visual indication of the ring. Remaining part of the circuit is the audio ringer based on IC1 (BA8204 or ML8204).... (added 10/05)
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