NEC B64‑U20 KSU any use for old phone collectors?

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Greetings all, were re-cabling an old office building and wile cleaning up a phone / network closet I saved a NEC B64‑U20 KSU from the recycle bin.
Does anyone have any experience with these?

Looks to be an electronic key unit.
I just found a manual online and skimmed thru to find the cards that are in it, there is the typical FXO (Foreign Exchange Office) cards for the incoming POTS lines and a digital line card for the proprietary NEC electronic office phones.
But then I see these two SLIB(4)-U10 analog line cards that appear to be analog FXS cards.
It appears to be just a tip and a ring to wire the phones.

I am curious if it would work with regular old phones, probably touch tone if any at all.
Thanks in advance

Cheers

[5415551212]

I wanted to update my old thread just in case someone comes across one of these.
The PBX system I have called a 'NEC Electra Elite IPK II' and I finally got around to testing it, it can indeed work with standard old phones we collect such as 500's and 2500 sets.
I am posting this because compared to other office phone systems of the era these are pretty compact, about the size of a old PC computer and these are largely considered scrap by Business Phone providers but might be useful to the more technical phone collector as with the right cards you could power up over 50 analog phone lines.
These are often left abandoned in office buildings when tenants move out and just end up in a dumpster or e-waste so I thought I'd share my notes here in hopes to help others in the future:

The unit has a beefy power supply, back up battery, and 10 card slots, the first two cards are the the main 'CPU' boards, there are 8 card slots for various interfaces.
The earlier IPK model used a CPU and a helper card called a  Multifunction Circuit Card card (MFIM),the IPK II has just one CPU card.
Cards are interchangeable between IPK and IPK II
The basic cards you need for it to work like a simple PBX are:
* SLIB = Single Line cards provide Foreign Exchange Subscriber (FXS) line ports, power and ringing for your phones.
* COIB = Central Office Interface cards provide FXO ports, To receive POTS Trunks, outside lines, an ATA or other PBX.
* ESIB = Electronic Station Interface, this provides a digital line to a NEC office phone, like other PBX's you may want at least one office phone for programing.

There were may other cards offered for this system for different features, voicemail, caller id, expansion, and networking functions. Probably the most common card to connect to the telco other than the COIB was the Primary Rate Interface T1 (PRT) card.  Newer cards exist like the 'Packet Voice Application (PVA) Card but it apparently requires a 'license key', it appears to be FPGA based which is interesting.

There are at least 2 types of the SLIB cards, most have 4 FXS voice ports, some have a add on card with A single Line Interface Expansion (SLIE) to give you 4 more ports per card.

My understanding so far is the NEC Electra Elite could be configured with 7 SLIB cards that have 8 FXS ports each, and you'd want card to connect to the the outside world so thats
8 FSX per card X 7 slots = 56 Phone lines.
And the ringing, pulse detection and such are top notch.

The PBX has 3 RJ21 female ports, 3 RS-232 DE9 ports, and a RCA jack for music on hold.
So if you salvage one you'll also want to grab the male RJ21 connector/cable and the 66-style punch down blocks.

Programing can be done four ways

• via a office phone, Programing via a office phone is simple just make sure the display phone works, the 'Dterm' office phones apparently  suffered flawed chip that drives the display it tends to fail, so if your getting a 'Dterm' office phone make sure the display works. Another issue is you waste an entire slot for digital office phone!
  
• Serial console connection via 'screen' on Linux or Putty on windows,I was able to get a serial console with:
  Port to use: COM 1 (DE-9 on the KSU chassis, not on the CPU card)
  Cable: Standard RS-232 straight-through DB9 cable to USB-serial adapter
  Switch setting: On the CPU II board, set SW3-1 = ON (RS-232C Monitor ON)
  Terminal settings:
  Baud rate: 38400
  Data bits: 8
  Parity: None
  Stop bits: 1
  Flow control: None
  running HELP shows a long list of commands 
  
• NEC dealer windows software 'PC Pro' on a windows host connected to the serial port, this seems to be unobtainium vaporware, if anyone has this please put it on archive.org.
  
• The CPU II card has a web interface. Unfortunately these are so old not that the web interface is quite fragile and had has a buggy java-script validator so hit and miss in a modern browser,
  the default IP address after a factory reset is 172.16.0.10, and it does not run DHCP so one needs so be on a LAN that can reach 172.16.0.10, like a old router with DHCP set to 172.16.0.0/24
  

Well thats all for now