...what was this WE #150A CSU used for?

[Babybearjs]

I came across this on Ebay, seller is in NYC. its a #150A CSU. what was this used for and why?

[FABphones]

eBay link: https://www.ebay.com/itm/164731370837 and screenshot of listing.

[rdelius]

It might be a voice coupler with an attenuator 

[Jim Stettler]

I looked up 150A CSU using google search in the TCI library.
It is for transaction network transmission.
It sounds like it is for  credit card machines and check verification.
Jim

[paul-f]

Well done, Jim.

The reference leads to this BSP:

https://www.telephonecollectors.info/index.php/search?q=314-100-010

[Babybearjs]

Interesting! something I have no need for.... are these even still used today? or has this feature been built in to the equipment now....