Not knowing the specific capabilities of the NEC PBX, may I suggest you take a look at the following url. It discusses the general problem around fxo disconnect problems, and shows different ways to solve it. Hopefully one of these methods will work for you.
This document is an early notification of a behaviour change that will be introduced in IOS XR release 6.5.
IOS XR configuration principles relevant for this article are:
On router platforms all interfaces must be by defaul...
With XR 4.2.0 the ASR9000 is releasing a new line of hardware models. This amongst others is the RSP440, the next generation RSP with faster switch fabric along with Typhoon based Linecards, the next generation network processor.
The Cisco EPN system incorporates a network architecture designed to consolidate multiples services on a single Multiprotocol Label Switching (MPLS) transport network. This network is designed primarily based on Application ...