Telephone LED status indicator
This will monitor telephone status without loading
the telephone line, this way if you have two
phones in parallel you will know if one of them is
busy. Connect the two ends of circuit in parallel
to phone lines.
Another circuit i designed with only diodes,
these are used as gates. This was also used in
some printer port switches i made.
High speed data switch
D1 to D4 make a bridge so that LED's are powered
in correct polarity. LED1 indicates line ok no
broken line, LED3 can light only when a 12V Zener
breaksdown, this shows if line is busy or free, so
that you dont go online when someone is talking on
the phone in another room. LED2 lights on an
incoming call ringing signal. This is a higher
voltage at least in older exchanges, so the cap
protects the LED, and LED Lights when a AC ringing
signal occurs. D6 protects LED2 from reverse
The Source file is here del00003.zip
I used to use this in the DUN or Dial Up Networking
days. A 386 computer and a Gateway 2000 Plugin Card
Modem. Maybe 14400 bps transfer
speed. It was the Netscape Browser like 3.6 light
to 4.7 for better machines.
This was the best page WinSock
Applications Pages On The Web. The above
device helped me know if the connection dropped due
to the extension or a power glitch.
Here is another circuit with just diodes - Edison
Bulb Life Extender
Notes - Components Selection - 05
Selecting the parts for your product design,
choosing the components intelligently is a part of
Product Design Engineering.