USB adapters and modems (was: Re: Hans Camenzind, Inventor of the 555, dies.)

On Fri, 17 Aug 2012, Fred Cisin wrote: I've had extremely good results with some of the USB 'adapters' (true serial ports with a USB interface, basically) that use the FTDI FT232B chip. They even have board designs and the driver source code available if you want to build it yourself. http://www.ftdichip.com/Products/ICs/FT232B.htm I have have replace some Sipex SP213EHCA RS232 transceiver chips in several of these devices with Maxim MAX213EAI parts. The Sipex transceivers are supposedly rated for +-15KV ESD, but my experience with them seems to indicate that they really aren't worth squat. On the other hand, the pin and function compatible replacement parts from Maxim are still working flawlessly. To me at least, the Sipex part looks to be a cheap knock-off of the Maxim part. As far as modems go, MultiTech and the USR Courier are two of the best. I'm not sure which MultiTech models support which DTE data rates, but with the Courier modems, if you have a 25MHz model, you can drive them at 230400 baud DTE, which came in handy if you are using V.90 and hardware data compression. I used them with Digi serial hardware to get those speeds. Before I had broadband, I used two of those modems paralleled up. Some of the late model USR Sportster modems can also be flash upgraded, but unlike with the free updates for the Courier modems, USR thought they could turn the less expensive Sportsters into a cash cow and didn't make the upgrades freely available (inkjet printer syndrome), with the sole exception of the modems sold with the X2 firmware already in them. That said, if you knew what you were doing, you could flash upgrade the late model 33.6 modems that had flash memory chips in them with the very same V.90 firmware that the X2 modems could use. It has been a very very long time since I did any tinkering with Courier and Sportster modems, but just last week I ran across my files for these, including the firmware updates and the 'unofficial' update utilities for the Sportster modems. As a side note with the USR Courier modems...when the electrolytic capacitors used in the power supply section of these modems begin to age (they get hot in normal use since the modems don't have forced air cooling), the modems will begin to emit digital "noise" (hissing/buzzing) via the internal speaker. There are no form-fit replacements for those capacitors, but I did find some which can be turned sideways that fit and work perfectly. The replacements probably have a longer life, too, since they aren't size-reduced and limited in height. If someone needs this information, I can dig through my notes for the part numbers.