Multi-Tech MultiModem EDGE Reference Manual page 253

•
If the <type> is changed while a call is ringing (RING URC) or active, the ME returns OK, but the new melody
does not take effect until after the call has ended.
• Users should be aware that when using this AT command quickly after "^SYSSTART" a "+CME ERROR:
operation temporary not allowed" is received. The audio data may not yet be accessible, resulting in a short
delay (less than 400ms) before the requested AT command response is returned.
Multi-Tech Systems, Inc. AT Commands for EDGE Modems (S000371G)
Chapter 16 – Audio Commands
253