Editing EMI (protocol) (section)

== Technical limitations ==

The two-digit ''transaction reference number'' means that an entity sending text messages can only have 100 outstanding messages (per session); this can limit performance, but only over a slow network and with incorrectly configured applications on one's SMSC (for example one session, with number of windows greater than 100). In practice it does not have any impact on delivery throughput.

The EMI UCP documentation does not specify a default alphabet for alphanumeric messages after decoding from hex digits. (It specifies an alphabet of [[ITU T.50 | IRA]] for the ''encoded'' message, which is the same as 7 bit [[ASCII]] as 0-9 and A-Z are [[ISO/IEC_646|invariant characters]]). The related ETS 300 133-3 standard specifies the [[GSM_03.38|GSM-7]] alphabet, which accommodates more languages than ASCII by replacing unprintable [[C0_and_C1_control_codes|control codes]] with additional printable characters. In practice the GSM-7 alphabet is used. Other encodings, such as [[UCS-2]], can be sent by using a transparent message and specifying the [[Data Coding Scheme]].