There was a concern (I don't understand) the candle stick > phones of that time would sense an erroneous pulse that > would confuse SxS gear, thus the 11 code. Why this=20 > wouldn't screw up panel gear I don't know. Once 'sticks=20 > went away the issue was moot.
It's possible to make a false preliminary pulse with any analog phone, not = just candlesticks. A false preliminary pulse equates to dialing a 1 no matter w= hat kind of equipment is at the other end, even ESS. As we've discussed on thi= s list any number of times before, an experienced high school kid can dial any num= ber by punching the switchhook button.
If you don't understand how this could happen, see
formatting link(my contribution to the November 2002 iteration of this discussion).