c5738d67__Codes___Telecomuserguides_com__Explanation
[0] 270 [Action] If the event occurs many times, unplug the telephone, wait for 3 minutes, then replug the telephone. Check the external lines. [Explanation] 
The system is dealing with a multi-byte message that it does not understand, while trying to initialize the telephone. May be caused by a noisy line.
Nortel Systems User Guides, Nortel Error Codes - Telecomuserguides.com
Explanation