There are 3 possible causes for getting a +CMS ERROR: 513

• The MS (jindi sms modem) loses the radio link (or the network requests an RR disconnect)
• The MS (jindi sms modem) does not receive the acknowledge from the network (CP_ACK) about 28s after the transmission of the Short Message data (CP_DATA)
• The MS (jindi sms modem) does not receive the acknowledge from the network (CP_DATA(RP_ACK)) about 42s after the channel establishment request