Customer has CICS unit that intermittently cannot be heard -voice or DTMF-. Could not duplicate.., cycled 25 calls through line and all were OK. Only recent error codes were 693-blah blah blah. Couldn't locate error code in any manual. Anybody think it's related? Any one know what 693- is? Also is there a DTMF or similar CPU test? Any help will be appreciated. I don't want to order a KSU without trying anything else.