Archive for the ‘Digital’ Category:

2019-04-06 HP Transmission Test Set

from FB group Bell Telephone of… Apr 6 (I bought a transmission test set, TTS-4, photo at bottom.) Glenn Peters We had a HP 493something transmission test set for testing up to 56 kb/s lines. I remember seeing the symbols on the green screen, like a carriage return would look like a little ‘CR’. The

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2017-11-21 Phones And Line Levels 

From FB group Bell Telephone… In the days of analog phones like 500s and 2500s, Ma Bell had the phone matched to the line, so whatever the line length was, it compensated and the signal levels were very uniform, it worked great. Then came along the full duplex digital system, and everything went to hell.

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2017-09-19 Giant ‘Analog Meter’ For Clock Display 

FB comment “Brilliant!” Preet Sangha said, and I agree, but since I have a hard time seeing small meters across the room, I thought up another, bigger meter.  How about this? Instead of meters, use a printout of a meter face, full page size.  There will be one for each hour, minute and second.  These

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2017-08-07 Protoboards And Bypass Capacitors

From FB post One important thing that people forget to do is consider what might happen with a circuit that has anything that draws power from the protoboard. If you’re working with a few low power devices such as small LEDs and switches, then there is usually not a problem. But if you have a

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2017-08-06 Seeing Digital Signals

From FB post about Arduino driving a ‘HC595 chip. You don’t need an oscilloscope to see digital signals.  If you slow down the speed, you can see what’s happening by looking at LEDs.  Everything is digital, just on or off. Plug two red LEDs, transistors, and current limiting resistors for LEDs (330 ohms), and for

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2017-01-18 Simulating An Analog Meter

A detector or discriminator in an electronic device might need to be adjusted to a very few points on a scale of a hundred or more points.  A digital indicator typically indicates only a fraction of that, possibly 16 points.  This is why the analog meter is still useful: it can indicate a small change

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2014-09-23 Germanium Transistor Technology

Paul is experimenting with a Joule Thief using some germanium transistors I sent him.  I thought about a few quirks of germanium transistors that I may not have (or may have) blogged earlier. The vintage germanium transistors were made at a time when the solid state manufacturing technology was much less advanced than it is

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2014-06-01 Remote Control Keys Go Intermittent

Something like a year ago I just took a cheap universal remote control that I often use and opened it up and unsoldered the IR LED.  I soldered a few feet of speaker wire into its holes on the circuit board and then soldered the LED onto the other end of the wire.   I mounted

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2013-11-01 TP3051J Telephone CODEC IC

Here’s a pic of a TP3051J telephone interface chip (CODEC and Filter).  Yes, a picture of the actual chip inside of the IC, after I popped the top off of it.  I have a lot of them so I figured that checking one out to see what was in it would be fun. The pic

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2013-04-03 Siemens DL 2416T 4 Character LED Display

This is from the 1980s, it’s all red LED segments or dots.  I tried to find an angle where the ceiling light would not show, but because it’s a bubble lens, just about any angle had that white  reflection.  The specifications are available on the ‘net.  The box outlined in red is one of the

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