I have lived in Chicago for 12 years and have yet to visit a Chicago Public Library. I’ve been missing out, there are quite a few awesome books, magazines and DVDs.
Apparently the Chicago Public Library uses Nortel Meridian Digital Centrex for their libraries. Centrex, was developed by ATT during the early 1960s to bring simulated PBXs to users without the user having to have dedicated equipment on site.
How it works is that the PBX functions are stored on the main switch at the central office. A company at a remote end then can dial 3,4,5 digit extensions and use features “internally” on their own private network with the processing being located at the phone companies main office. To reach an outside line to be connected to the private network you would dial “9.”
The big advantage of this setup was you could have many buildings across town or across the state that could dial in between locations using internal dialing without paying long distance.
For early Multi Line sets pre dating digital telephony, 1A2 sets generally handled multi line applications, in the case of multi internal lines, 4 or 5 digit internal extensions would be tied into the line buttons. To dial outside on those lines, you’d dial 9.
Starting in the late 1970s with the introduction of digital centrex, P phones were introduced. The phones with the Nortel DMS 100 version resembled SL1 telephones but were actual analog sets with computer controlled multi line capability.
Here in Chicagoland Centrex has been extremely popular with Chicago City Government, Chicago Public Library, State Government of Illinois, University Of Illinois, and Harris Bank.
I posted a question on Tek Tips for someone to give me a little more information about these phones. Apparently even though they represent digital phones, all of the signalling is analog….see the screen shot below from Tek Tips:
They M5316 and M5008 telephones were introduced somewhere around 1995 to replace the earlier “delta” flat board styled Nortel M5112 and M5009 sets. The earliest docs I could find for the newer Aries II styled centrex phones are show on the photo below:
This M5008 was sitting at the reference counter. The Red Triangle is inactive on these sets and is blacked out. I never understood other than the fact that these phones are line powered (no AC adapter) and can show multiple DN appearances, but not much more power than that, most likely not enough to even illuminate the red LED triangle. There is a one way speaker which allows one way listen on hook but no Handsfree talk back.
Next are the M5316s that were on the main desk. These sets are twins of the M2616 sets and do contain more features such as a LCD display, Red LED triangle, Full Handsfree and adjustable display functions via the Program button. The features I mentioned above only work when the phone is connected to a power spiller that plugs into an electrical outlet. From the outlet, the power then travels from the AC adapter via a standard telephone cable to provide just one telephone cable to the desk telephone. If the phone loses power, dial tone and line buttons still work, but Handsfreee and the LCD display do not work.