bmk@mvuxi.att.com (Bernard Mckeever) (09/13/89)
I sure enjoyed Larry Lippman's SXS article the other day and got a kick out of his explanation of BMF technology for digit absorbing selectors. Larry and others mentioned dialing situations where the digits would be absorbed over and over, I have seen this happen but it was always a trouble, and resulted in wrong numbers or not enough digits. Let me explain. The level 7 tandem office I worked in had 2nd selectors set up to absorb digits 2,3,4, and 7. The switch would only allow a digit [any digit] to be absorbed once. If the exchange you were calling was 733 you could dial 743 and still get the right party. On outgoing calls all levels except 7 and 6 were routed to the appropriate toll or stepper tandem office by the first selector. Level 6 calls went to a group of special selectors that routed 61X calls to the test board, repair bureau, or test connectors in the office. level 62, 63, 64 .....etc. routed to the level 6 tandem trunk groups or vacant code announcement. Level 7 calls had several available routings. 71 vacant code 72 absorb 73 " 74 " 75 third selector 76 route to end office 77 absorb 78 route to end office 79 route to end office 70 vacant code Lets get rid of the 75 calls first. There were 3 separate offices that had 75 as the first two digits of the office code. The third digit was required to identify the correct trunk group for the end office. With the 4 groups left, the 3rd digit [still on the 2nd selector] would cut in on any level dialed. This is the only way to direct the call to the proper connectors for call completion. In this office anyway. Incoming calls were treated much the same. All level 7 calls entered on a digit absorbing incoming 2nd selector, except some trunks from the 3 offices using office code 75X, and were treated as above. The trunks from the 75X offices would come in on a non absorbing 2nd selector if the 2nd digit had been a 2, 3, 4, or 7. I should restate, this was a level tandem office, not an end office. Also the arrangement of the 75X offices was not a normal one. End offices had different arrangements that could allow 4, 5, and 7 digit dialing arrangements. I have no doubt that some offices will allow a few designated digits to be absorbed over and over, but I just was not lucky enough to work in one. PS. If anyone reading this is going to be at the NCF in Oct. and would like to get a look at some modern digital transmission equipment located nearby let me know. Bernie McKeever 508-960-6289 BMF