AWalker@RED.RUTGERS.EDU.UUCP (01/21/87)
There have been an awful lot of queries about hold circuits and line-in-use indicators! The former has probably been hashed to death; the latter involves some subtleties which the reader should be aware of. DAK's little box with an LED in it probably doesn't do proper isolation between the line and the indicator circuit; the workaround to avoid AC hum is obviously the 9 volt battery and the plastic box. Using a wall transformer thus may lose slightly if there's enough AC noise coupled through the transformer from the AC line. *Any* piece of telephone equipment that electrically comes anywhere near ground or AC wiring needs good isolation or you get lots of hum. A simple line-in-use is (an LED in parallel with 100 ohms) in series with a given phone unit. This passes a nominal 15 mA or so through the LED, lighting it. For a system of more phones you could substitute the input side of an optoisolator for the LED and hang some more involved circuitry off that. The opto will provide the necessary ground isolation, so you can do whatever you want after it. Post office codes: I called my local distribution office to inquire if placing the bar code on my personal mail would speed it up any. Answer: no. All incoming mail is passed through the OCR anyway, and if the OCR can read the last line of the To: address [precluding presence of Attention lines and other things after the line containing the zipcode!], it ink-sprays the barcoded zipcode on the piece if there isn't one already. Bulk-sort stuff like business reply envelopes have those hash marks on the right side which form one of four or so recognition codes and tell the machine what kind of mail it's seeing. It can then optionally handle these pieces differently. Mail addressed with high-contrast typed print, or *very* neat handwriting in dark ink, has a good probability of being seen by the OCR. Those pieces that fail go to the human sorters; the post office is continually trying to make these sorters smarter and smarter and eliminate the maximum humans from the processing. The person I talked to is quite willing to let me come down and tour the facility; I think I'm going to accept. Equal access carrier dialing: Ship a copy of <awalker>equal.access from site red.rutgers.edu. I can mail it if necessary. 50-pin multiline phone connector: Ship a copy of <awalker>ktu.block from site red.rutgers.edu. I can mail it if necessary. _H* -------