User Manual
GSM/GPRS Module Series
GC10 Hardware Design
GC10_Hardware_Design Confidential / Released 52 / 76
3.10. PCM Interface
GC10 has reserved PCM interface, it is used as digital audio transmission between module and customer
device. This interface composes PCM_CLK, PCM_SYNC, PCM_IN and PCM_OUT signal lines. PCM
function is not supported at present.
3.11. Behaviors of the RI
Table 14: Behaviours of the RI
If the module is used as a caller, the RI would maintain high unless 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 36: RI Behaviour of Voice Calling as a Receiver
State RI Response
Standby HIGH
Voice Call
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 [10].