Specifications

TC35 / TC37 Hardware Interface Description
TC35_37_HD_02_V03.10 - Released Page 50 of 92 21.12.2001
1s
/
RING0
URC
3.8.2.3 Behaviour of the RING0 line
The behaviour of the /RING0 line depends on the type of the call received.
• When a voice call comes in the /RING0 line goes low for 1s and high for another 4s.
Every 5 seconds the ring string is generated and sent over the RXD0 line.
If there is a call in progress and call waiting is activated for a connected handset or
handsfree device, the /RING0 line switches to ground in order to generate acoustic
signals that indicate the waiting call.
Figure 20: Incoming voice call
• Likewise, when a Fax or data call is received, /RING0 goes low. However, in contrast to
voice calls, the line remains low. Every 5 seconds the ring string is generated and sent
over the RXD0 line.
Figure 21: Incoming data call
• All types of unsolicited result codes (URCs) also cause the
/RING0 line to go low, however for 1 second only.
For example, the GSM engine may be configured to output
a URC upon the receipt of an SMS. As a result, if this URC
type was activated with AT+CNMI=1,1, each incoming
SMS causes the /RING0 line to go low.
For more detailed information on URCs please refer the
"TC3x AT Command Set".
Table 17: Ring signal
Function Pin Status Description
= 0 Indicates an incoming call or URC. If in
SLEEP mode, the cellular device
application is caused to wake up.
Ring indication /RING0
= 1 No operation
4s
/RING0
4s
1s
1s
1s
Ring
string
Ring
string
Ring
string
5s
/RING0
Ring
string
Ring
string
Ring
string
5s