As 2821 running IOS 12.4(24)T8 is repporting:
CURR STATE : (busy)inuse (b-out)busy out (bpend)busyout pending
LEGEND : (bad)bad (shut)shutdown (dpend)download pending
I figured out that it is necessary to install dsp_c5510_flex.rbf reading "Identify, Supersede, and Maintain Compatible DSP Firmware Version Levels on C5510 DSPs".
http://www.cisco.com/c/en/us/support/docs/voice/voice-quality/109469-dspware-c5510dsp.html
From where is it possible to download dsp_c5510_flex.rbf ?
BUG CSCsd54344
DSP: Persistent echo heard on c5510 DSPs with 4.4.13 DSPware or higher
