On 28 March 2015 at 01:32, Justin Richards wrote: > Russell said: > > My long ago holiday work showed me that at 50 VDC on a humid day you ge= t > > annoying shocks on the back of your hands if working on > > I would find this very frustrating. Some of our DDF's and pillars were > arranged so the shock would cause the hand to fly back crashing into chee= se > grater like solder tabs and in panic quickly withdrawing removing skin on > the way. > That's the one :-). NZPO holiday job. Main Distribution Frame in telephone exchange. All customer telephone lines have a twisted pair run from their incoming cable pair termination to the corresponding equipment side termination. Wiring blocks have "tags" on one side from incoming cable and on other side for Jumpers. Frame is 10+ feet high and lonnnnnnnnnng with rail-suspended rolling ladders for access for soldering. Space between blocks is as close as they feel is "reasonable" to minimise frame size. Brushing tags on adjacent block happens constantly. 50V when humid is annoying. Very occasionally you get "ringing" voltage. Far more painful. (AFAIR 70 VAC on top of 50 VDC so about 150 V above ground peak. Remembering not to leap off a ladder come what may is a desirable survival trait. To the cheese grater effect add the occasional hot solder splash - try to remember you are using a large and hot iron when you react to a shock :-). Interestingly, of the various possible jobs in the exchange, of which the others were all more technically complex, I most preferred jumper running. My general nature does not respond well to mindless repetitive rote jobs - but maybe the jumper running allowed the mind to wander far afield as I worked due to its extremely standardised nature. Until a burst of ringing arrived :-). The ultimate exchange "treat" was managing to contact the open rear contacts of a "Buttinski" field phone as you pulled it out of the jack on a step by step selector switch at the moment that the switch "homed". Very very nasty inductive kick, repeated. Russell --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .