One Door, 4 Stakeholder Systems

Can you assign each group their own facility code and then let all 4 facility codes be read on the door's reader?

Its a part of a large multistory facility with four international tenants. There is a common lobby for all tenants and eventually, this lobby will also feature a common optical turnstiles into the elevator lobby. 

We have had this type of request many times and it can be a lot more difficult to implement than it first appears.

The cleanest solution is to install an access control system that has a "segmentation" feature, sometimes called a "tenant" feature. Each segment acts as its own virtual access control system and the individual tenants would each be assigned their own segment. Shared doors (such as the front door) would be assigned to all segments. Doors on individual floors occupied by stakeholders would be assigned only to their own segment.

Most of the major manufacturers support segmentation, but be sure to work out the details before purchasing a system. There are lots of potential "gotchas" to watch out for.

It is also possible to connect a single card reader to two or more separate access control systems using an Intelligent Wiegand Splitter. These devices look at facility codes and then direct the Wiegand signal to the appropriate system. I have never seen a successful implementation of this but see no reason why it wouldn't work. I have seen attempts to do this with less sophisticated splitters and these never worked well. (Cards from one system read as "invalid access attempts" on the other system and vice versa.) Hopefully the use of an intelligent splitter would solve this problem.

This is a PDK ProDataKey feature of the cloud product.  I don’t work for PDK but i’ve seen it demonstrated.  

If these are international customers they probably want to have their own access control system tied into their system.  One thing we have done is just put in wiegand splitters so one reader can go to multiple systems.  The downside is you will get a fair amount of unknown card alarms which you can have most enterprise level systems ignore and just log instead of generating alarms.

RBH has the option to divide cardholders in "Companies". Based on the login credentials to the software a stakeholder would only be able to see the cardholders in their "Company". Setup this scenario with two stakeholders in a warehouse/office building where the office people wanted to have full control of their doors and the warehouse wanted to have full control of their doors, some of the doors where shared. Worked great and I don't know of any reason the concept wouldn't be able to scale up to 4 stakeholders. In this install the cardholders where totally isolated, the warehouse folks couldn't see the office cardholders and visa-versa, even in history reporting.

I would think most major access control offerings would offer similar functionality.

i was looking though the posts and suddenly it occurred to me that i had this problem before and solved it easily. But that was 12 years ago and being a bit older than most folks, I could not recall the product. After digging though some old project records without success,  I reached out an old friend in NYC (integrator)  who reminded me of this product . Has anyone had experience with this? I used this product in a long time ago and its still in today.

 These are all international companies with thousands, of doors and hundreds of thousands of credentials. Solutions that require new systems are pretty much off the table.