Bells on terminals (was: Re: YouTube videos of ASR33, etc.)

The discussion of bells on terminals reminded me of a weird experience. I had built up a terminal using a Qume printing mechanism (Sprint 4 interface) and added a keyboard and UART to make it complete. The printer didn't have a "bell" so I had to make one. In looking around for a nice tone to use, I found the one from the baud rate generator (MC14411). Since I was using an ASCII sequence, I had little use for the 134.5 rate (it is used for IBM 2741's) so I picked it up and with the use of a (couple?) one-shot, I made it into the beep. It was 16x the rate, so the tone was 2153.3Hz (see the data sheet). It worked quite nicely, and was pleasant sounding enough. Both control-G's and I were happy. Then the terminal was hooked up to an acoustic modem. While this isn't bad in itself, the astute among us will note that the tone for the bell is very near the center of the passband (2025-2225Hz) of the originate modems detector. So, every time someone sent a control-G to the terminal ALL sorts of weird things happened. Needless to say, I changed the wire to a different tap on the MC14411 baud rate generator chip. Yes, hardware can have unexpected bugs. Somewhere I still have this terminal. Daisywheel printers were fun to play with. I have the schematics somewhere if anyone needs info. -- Sorry, No signature at the moment. ____________________________________________________________________________________ Be a better friend, newshound, and know-it-all with Yahoo! Mobile. Try it now. http://mobile.yahoo.com/;_ylt=Ahu06i62sR8HDtDypao8Wcj9tAcJ