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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)
