As per your need, I am giving you list of the core companies of in area of electronic and communication engineering.

Government Companies in India

SAIL
HAL
UPPCL
NTPC
ONGC
EIL
BHEL
Bharat Electronics
TERI
GAIL
BSNL(bharat sanchar nigam limited)
ISRO(Indian space research organisation)
DRDO(Defense research and development organisation)
ECIL(Electronic cooperation of india limited)
AAI(Airport authority of India)
RRB(Railway recruitment board)
IES services

Following are the

SAMSUNG.
L.G.
VIDEOCON.
SIEMENS.
PANASONIC.
SONY.
INTEL.
JINDAL INFOTECH.
TCS.
RELAINCE COMMUNICATION.
BAJAJ ELECTRONICS.
PHILIPS INDIA.
AIRTEL BHARTI.
MOTOROLA
NOKIA.
Samsung
Hyundai Electronics
Finolex Cables
Emco
Philips India
Havells India
Solectron Centum
Hindustan Cables
Surya Roshni