What protection do you use with VG224s?

[tdennehy]

We have many VG224s in production.  Nearby lightning strikes kill ports on the VG224.

The cabling has protection on it - from the old Western Electric 701 PBX.  However, that switch delivers 52 volts at 39 milliamps, and the Cisco VG224 is much lower.

The protection on the cable plant was designed for the Western Electric switch.

What is the best practice?  When changing out PBXs for VGs, do we have to change out the protection, and if so, what is recommended?

[Karthik Sivaram]

Hello,

The VG224 is designed for on premises applications which is generally

for internal building use. If you are having issues with lightning strikes

blowing up the interfaces, then it appears that you are using the VG224 as an Off

Premises Extension  with long/exposed cable runs which are susceptible to

picking up RFI and EMI. The VG224 was not designed to be used for OPX use and

we would not be recommending it in environments where cable runs are exposed to

lightning even with external protection.

Normally you would use an external line driver/isolator to drive the long

distances and provide isolation/protection. These are often called Long Loop

Adapters. Here is an example -

http://www.telcom-data.com/products/VIK-LLA-1.aspx

Our newer FXS modules support an "OPX lite' mode which drives longer distances

and has better protection -

http://www.cisco.com/en/US/solutions/collateral/ns340/ns517/ns477/ns296/application_note_c27_461821.html

Hope that helps!

Regards,

Karthik Sivaram