Users Manual

GSM/GPRS Module Series
M66 Hardware Design
M66_Hardware_Design Confidential / Released 58 / 82
3.13. Behaviors of The RI
Table 21: Behaviors of the RI
If the module is used as a caller, the RI would maintain high except the URC or SMS is received. On the
other hand, when it is used as a receiver, the timing of the RI is shown below.
Figure 33: RI Behavior of Voice Calling as a Receiver
State RI Response
Standby HIGH
Voicecall
Change to LOW, then:
1. Change to HIGH when call is established.
2. Use ATH to hang up the call, RI changes to HIGH.
3. Calling part hangs up, RI changes to HIGH first, and changes to LOW for
120ms indicating “NO CARRIER” as an URC, then changes to HIGH again.
4. Change to HIGH when SMS is received.
SMS
When a new SMS comes, the RI changes to LOW and holds low level for about
120ms, then changes to HIGH.
URC
Certain URCs can trigger 120ms low level on RI. For more details, please refer to
the document [1]