{{refimprove, date=March 2019 External Machine Interface (EMI), an extension to Universal Computer Protocol (UCP), is a protocol primarily used to connect to short message service centres (SMSCs) for

mobile telephone A mobile phone, cellular phone, cell phone, cellphone, handphone, hand phone or pocket phone, sometimes shortened to simply mobile, cell, or just phone, is a portable telephone that can make and receive calls over a radio frequency link whil ...

s. The protocol was developed by

CMG CMG may refer to: Companies * Capitol Music Group, a music label * China Media Group, the predominant state radio and television broadcaster in the PRC * China Media Group Co., Ltd., publicly listed Chinese holding company in the media sector * ...

Wireless Data Solutions, now part of

Mavenir HRMavenir Systems, Inc. dba Mavenir is an American telecommunications software company, created in 2017 as a result of a three-way merger of existing companies and technologies, that develops and supplies cloud-native software to the communicat ...

Syntax

A typical EMI/UCP exchange looks like this : ^B01/00045/O/30/66677789///1//////68656C6C6F/CE^C ^B01/00041/R/30/A//66677789:180594141236/F3^C The start of the packet is signaled by ^B (STX, hex 02) and the end with ^C (ETX, hex 03). Fields within the packet are separated by / characters. The first four fields form the mandatory header. the third is the ''operation type'' (O for operation, R for result), and the fourth is the ''operation'' (here 30, "short message transfer"). The subsequent fields are dependent on the operation. In the first line above, '66677789' is the recipient's address (

telephone number A telephone number is a sequence of digits assigned to a landline telephone subscriber station connected to a telephone line or to a wireless electronic telephony device, such as a radio telephone or a mobile telephone, or to other devices f ...

) and '68656C6C6F' is the content of the message, in this case the

ASCII ASCII ( ), abbreviated from American Standard Code for Information Interchange, is a character encoding standard for electronic communication. ASCII codes represent text in computers, telecommunications equipment, and other devices. Because ...

string "hello". The second line is the response with a matching transaction reference number, where 'A' indicates that the message was successfully acknowledged by the SMSC, and a timestamp is suffixed to the phone number to show time of delivery. The final field is the

checksum A checksum is a small-sized block of data derived from another block of digital data for the purpose of detecting errors that may have been introduced during its transmission or storage. By themselves, checksums are often used to verify dat ...

, calculated simply by summing all bytes in the packet (including slashes) and taking the 8

least significant bit In computing, bit numbering is the convention used to identify the bit positions in a binary number. Bit significance and indexing In computing, the least significant bit (LSB) is the bit position in a binary integer representing the binary ...

s from the result. The full specification is available on the LogicaCMG website developers' forum, but registration is required.

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 IRA for the ''encoded'' message, which is the same as 7 bit

as 0-9 and A-Z are invariant characters). The related ETS 300 133-3 standard specifies the GSM-7 alphabet, which accommodates more languages than ASCII by replacing unprintable control codes with additional printable characters. In practice the GSM-7 alphabet is used. Other encodings, such as

UCS-2 The Universal Coded Character Set (UCS, Unicode) is a standard set of characters defined by the international standard ISO/IEC 10646, ''Information technology — Universal Coded Character Set (UCS)'' (plus amendments to that standard), whi ...

, can be sent by using a transparent message and specifying the

Data Coding Scheme Data Coding Scheme is a one-octet field in Short Messages (SM) and Cell Broadcast Messages (CB) which carries a basic information how the recipient handset should process the received message. The information includes: * the character set or mess ...

Alternatives

* Short message peer-to-peer protocol (SMPP) also provides

SMS Short Message/Messaging Service, commonly abbreviated as SMS, is a text messaging service component of most telephone, Internet and mobile device systems. It uses standardized communication protocols that let mobile devices exchange short text ...

over TCP/ IP. * Computer Interface for Message Distribution (CIMD) developed by

Nokia Nokia Corporation (natively Nokia Oyj, referred to as Nokia) is a Finnish multinational telecommunications, information technology, and consumer electronics corporation, established in 1865. Nokia's main headquarters are in Espoo, Finlan ...

Syntax

Technical limitations

Alternatives

External links