DELHI METRO RAIL CORPORATION.LTD.
(A joint Venture of Government of India &
-Government of Delhi)
The basic components of telecommunication
department can be stated as follows:
FOTS ( Fiber Optic Transmission System)
PIDS (Public Information Display System)
PAS (Public Address System)
CCTV (Closed Circuit Television)
EPABX (Electronic Private Automatic Branch Exchange)
Operational Control Center (OCC)
Located at Shastri Park and Barakhamba.
It controls both Rail & Metro Corridor.
Here all the central systems of various systems are
All the train movements are supervised and system
monitoring equipments are installed in OCC.
Public Information Display System
It is used to display traffic &
train scheduling information
also data related to arrival &
departure time and other
information along the station and various platform
Public address system(PAS):
• It is used to broadcast voice messages to passengers/staff
in all stations , depots ,OCC and DMRC Headquarter.
•Also used for emergency evacuation broadcast .
Master Clock system:
Clock system is used to provide accurate time to
staff, passengers and time reference to systems at
DMRC. Accurate and synchronized time information is
obtained from Global Positioning System (GPS) by
Master Clock at OCC.
Closed Circuit Television System(CCTV):
•This is used to monitor the station and the platforms
along with the metro corridors where it is very difficult
to keep a view on the corridors.
•Mostly it is used for security reasons and help train
operators in the curved station platforms.
Electronic Private Automatic Branch
Exchange (EPABX) :
For purpose of planting communication link between
different stations, DMRC has its self-sustained
telephone exchange. This system works on -48 V DC.
Data is processed at a rate of 64k bps.
A radio uses electromagnetic waves to send information
across the air. This is accomplished by producing an
electrical signal that moves back and forth, or oscillates,
at a rapid rate.
Technology in use:
• Terrestrial Trunked Radio (TETRA) (formerly known
as Trans European Trunked Radio) is a specialist
professional Mobile Radio and two-way transceiver
• This standard was developed by the ETSI for private
mobile radio. Open standard for private mobile radio. It
defines radio services and interfaces
• The TETRA standard defines the air interface between
mobile stations and the infrastructure.
Radio system in DMRC
The Radio system is a digital trunked radio system,
operating in 380-400 MHz band and confirming to TETRA
The Radio system have central control equipment installed
The Radio system uses EBTS towers for communication
in rail corridor & leaky coaxial cable along each track in
the tunnels for communication with train borne mobile
radio (in metro corridor) .
The trunking concept allows channels or other
resources to be made available to users as they
are needed. It allows all the channels to be pooled
together. As a channel is needed, the controller
grants an available channel from its pool of
BR= Base Radio
In most organizations, radio users work in groups that
are based on their functions and responsibilities. These
groups of radio users can be assigned to communication
talkgroups that reflect their function or responsibilities.
Calls are semi-duplex.
TYPES OF MODES OF COMMUNICATION:
1. Trunk Mode Operation:
It represents communication
between two or more TETRA
mobile stations with the use of
trunking network infrastructure.
This mode consists of 4 communication modes:
(b) Private mode
(c) Phone mode
(d) Emergency mode
(a) Group Mode:
It is a half duplex communication
mode in which many users
can communicate with each
other by selecting a
common talk group.
(b) Private Mode:
It is a half as well as full duplex
communication mode in which many users
can communicate with each other
privately without interfering the talk group.
It uses two frequencies.
(c) Phone Mode:
It is a full duplex mode of
communication in which a radio
user can talk to any dialed
phone number within DMRC or
external network connected to DMRC.
(d) Emergency Call:
The emergency key is provided on
every radio equipment, an audio
visual alarm will appear on every radio unit in that talk
group. The party who initiates the call has
the highest priority for calling.
2. Direct Mode Operation:
• It represents direct communication between two or more
TETRA mobile stations without the use of trunking
• Simplex mode of communication.
EBTS (Enhanced base Transreceiver System )
• It provides RF interface from the master
site to the mobile subscribers in a TETRA
system. It can be categorized in two
(a) Above ground (Rail corridor)
(b) Under ground (Metro corridor)
•Both are of same configuration & characterstics.
Khyber Pass Depot
Pi i (E est
at am ast
W nc ura
La zir ave
K wra ur
ha c e
Pr nd P
Radio Base Station Site
Radio Base Station Site
Shastri Park Station
(at-grade or elevated)
Shastri Park Depot
A transmitter transmit radio signal
A transmitter usually has a power supply, an oscillator,
a modulator, and amplifiers
A receiver is a device that receives a radio signal
from an antenna and decodes the signal for use
Generally, receiver refers to a demodulator, a
preamplifier, and a power amplifier
Types of radio used in DMRC:
1. Mobile Vehicle radioFixed
(a) RAU (Radio Access Unit) or Zetron radio set or
(b) Train radio set
(c) RCW (Radio console workstation)
2. Mobile Portable radio
Each radio has its radio identification which register
itself in central system for its function. The radio is
programmed for its ID, frequency, network code, talk
group and allowing types of call.
Radio consists of
trans and receiver and frequency synthesizer circuit
Processor) for digital function.
RAU(Radio Access Unit)
It is located in the Station control room.
It is placed in the best radio coverage and it is fixed
& has a functionality just like a telephone radio.
It is ideally suited to radio operator dispatchers and
where office personnel need access to a radio system
without wanting to have a radio placed into the office
The M390 is a robust telephone style
desktop controller with a large ,easy
to read LCD display & handset.
MTM700 Mobile radio is installed at front & rear cab
for communication between the train driver &
designated station controllers at OCC & Depots.
This radio unit is connected to different units e.g.
TRIU,TRCP; these units are required to communicate
with RCW ,TIMS, ATS and rear cab radio.
Dome type omni directional antenna is located at top
roof of train. This antenna is connected through RF
cable which is connected to radio unit.
Radio console workstation
• It is for different controllers
that is working in OCC such
that chief and traffic
• On its MMI ,all the radio
information is displayed and
communication can be set up
only by clicking the radio
Hand Portable radio
The hand portables come with 3x4 keypads,
rotary switch dial, and LCD for number
dialing and maximum flexibility. Each hand
portable is equipped with an ultra high
capacity batteries (Li ion or Li Mgh.) for
longest standby and talk-time of 24 hrs,
that is 5% transmit, 5% Receive and 90%
Hand portable is suitable for all kinds of calls
used in DMRC.
Advantages of TETRA:
1. The frequency used gives longer range, which permits
high levels of geographic coverage with a smaller number of
transmitters, thus cutting infrastructure costs.
2.Unlike the cellular technologies, TETRA is built to do oneto-one, one-to-many and many-to-many.
3. Rapid deployment (transportable) network solutions are
available for disaster relief and temporary capacity
4. In the absence of a network mobiles/portables can use
'direct mode' whereby they share channels directly (walkietalkie mode).
Disadvantages of TETRA:
1. Requires a linear amplifier to meet the stringent RF
specifications that allow it to exist alongside other
2. Handsets are more expensive than cellular.
3. Handsets can sometimes interfere with badly
designed (usually old) or sensitive electronic devices
such as broadcast (TV) receivers, hospital equipment,
TETRA communication system has been implemented
The signals are clear
The voice clarity is excellent
The TETRA technology effectively meets DMRC’s
operational and functional expectations
In my training I have got to know about the different means
of communication systems used in DMRC. It consists of
radio communication techniques & radio systems; and data
transfer between stations and the OCC.
My presentation focuses on radio system. My conclusion
from this training is that DMRC uses two types of radio
a) Fixed Radio(Zetron, train radio, RCW)
Both have their advantages and disadvantages. Fixed radio
equipments provide better voice clarity, but can not be
moved when placed at a particular place. Similarly Portable
radio equipment can be moved from place to place, but
voice clarity may vary as device might not provide 100%
signal at all places.