1. DTETERMINALDTEis a terminal equipment that changes user information intosignals or reconverts received signals.
It is typically either a dumb terminalor the serial port on a computer/workstation. DTE does not interface withanother one, however it often communicates with a DCE. DTE includes any componentsthat works either as a source of or as a destination for binary digital datasuch as printer, terminal or any device that generates or receives digitaldata. 2. DCETERMINALDCEis a device that sits between the data terminal equipment (DTE) anda data transmission circuit.DCE carries out tasks such as signal translation, coding,and line clocking in a data station. A DCE takes data generated by a DTE,converts them to an appropriate signal, and then introduces the signal onto thecommunication link.
Same modulating method must be used by both sending andreceiving DCEs in order to send the data. 3. DTE-DCEINTERFACEInthe United States, most usual interface used to interlink I/O ports is theDTE-DCE interface. This interface is used in serial communications systems obeysthe RS-232C standard as published by the Electronics Industry Association (EIA)(Wickman, 1986, para. 2). A DTE-DCE interface involves both DCE and DTE deviceson one end and the other.
The DTE will generate the data and passes it alongwith any control information to a DCE on the same end. When the signal arrivesat the receiving end, the process is reversed.DTE-DCE Interface.Digital Image. Serial WAN Link. 20September 2009.
http://kb.guru-corner.com/admin/attachments/Cisco/cc_wan1j.jpg In order to define the connection betweenDCE and DTE has been made into many standards especially by EIA and ITU-T, who havebeen the most active organization involved in developing DTE-DCE interfacestandards. Each standard provides a model for mechanical, electrical,functional characteristics of the connection.
EIA standards include EIA-232,EIA-442, EIA-449 while ITU-T standards comprise of V series and X series. 4. EXAMPLESOF STANDARDSi. RS 232 STANDARD ISA 2 Port RS232. Digital Image. Retrieved fromhttp://www.
brainboxes.com/product/cc-523/isa-2-port-rs232 In 1960, RS-232 is a standard introducedfor serial communication transmission of data. EIA’s RS-232 or RecommendedStandard 232 as of 1969 defines the electrical signal characteristics such asvoltage levels, signalling rate, timing, and slew-rate ofsignals, voltage withstand level, short-circuit behaviour,and maximum load capacitance with digital signal, NRZ-L (NRZ) encoding.Pluggable connectors (male DB-25 connector on DTE end (cable has female) and femaleDB-25 connector on DCE end (cable has male)) and pin identification are used asinterface mechanical characteristics for the mentioned standard (Sanderson,2000).
The functionalstandards in RS-232 is most of the 25 pins have defined functions, few of themare normally used, mostly for control. Pin 2 is used for transmitted data(transmitted from DTE), pin 3 for received data (transmitted from DCE) and it canbe used for half or full-duplex. ii. ITU-T X.21 STANDARDX.
21device. Digital image. Retrieved from https://en.
X.21 pinassignments. Digital image. Retrieved from https://arcelect.
com/X21_interface.htm(right).Launched in themid-1970s by the ITU-T, X.21 (also referred to as X21) is an interface specificationfor differential communications. X.21 was first introduced as a medium toprovide a digital signalling interface for telecommunications between senderand receiver devices. This includes specifications for DTE-DCE physical interface factors, alignment of call control charactersand error checking, elements of the call control phase for circuitswitching services, and test loops (“X.21”, n.
d.). Thisstandard is a state-driven protocol running full duplex at 9600 bps to 64 Kbpswith subscriber networks (“The X.21 Interface”, n.
d.).As for themechanical aspects of this standard, it has got DB-15 connector and it usesRS-422A, a cable that length up to 1km. The standard maximum bps is inverse of thelength of cable used. For example, for 10m it has bit rate of 10Mbps and100kbps will be the bit rate for 1km-long cable. However, for digitaltransmissions, typically 64kbps is sent and received using this standard. X.
21has fewer control pins than EIA-232. Most pin assignments are in pairs to makeit balance for the balanced mode. The pin assignments reflect the mechanicaland electrical specifications (Sanderson, 2000). References1. Wickman, M.
X. (1986) Data communicationinterconnect device. Retrieved from https://www.google.com/patents/US4607170 2. Corner, G. (2009) DTE-DCE Interface.
Retrieved from http://kb.guru-corner.com/admin/attachments/Cisco/cc_wan1j.jpg 3. Sanderson, P. (2000) DTE-DCE Interface.
Retrieved from http://faculty.otterbein.edu/psanderson/csc465/notes/spring00/DTE-DCE.html4. X.21. Retrieved from https://en.
wikipedia.org/wiki/X.215. The X.21 Interface. Retrieved from https://arcelect.com/X21_interface.htm