RS-485 Cable Vs Shielded CAT5/5E

Hello,

I was quoted by an access control installer for a job. Part of the job was that we utilize OSDP readers and compatible controllers. The solution presented was HID iCLASS SE readers and Mercury EP1502/MR52 controllers.

Turns out they didn't quote out the right cable. OSDP isn't meant to run over the same cable as Wiegand. The recommendation in Mercury and HID manuals is for an "RS-485" cable for both the Mercury communication wiring and reader wiring. Something like THIS or THIS. Single twisted pair, 24AWG, and shielded. The problem is this cable cost $2/ft! And all the RS-485 cable I can find seems rather expensive. To me it looks like this should work fine with CAT5/5E/6 shielded cable. Does anyone have experience with this or know the answer?

The biggest difference I found from my googling was that RS-485 has a 120 ohm impedance vs 100 ohms with CAT. However the general opinion I found was that this wasn't really relevant or meaningful in 99.99% of applications. And I read at least 1 person say they use this instead for access control and cameras when RS-485 is recommended without any issue.

This is an unfortunate situation. We had gone over this quote for the past 3 months. A few weeks ago paperwork was signed and at least some money was exchanged. I requested some minor alterations unrelated to this cabling and that didn't alter cost while we waited for HID to issue us an Elite Key. No work has been done yet. I get an email telling me they made a mistake with the quote (the same one for the past 3 months) and needed to add the cost of this cable. A 17% increase in the quoted price. I'm trying to salvage the situation before it turns for the worse.

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