JTO Cheatsheet — Quick Reference

Frequency Bands

VLF (3-30 kHz)    — submarine comms
LF (30-300 kHz)   — AM radio (long wave)
MF (300kHz-3MHz)  — AM radio (medium wave)
HF (3-30 MHz)     — shortwave, amateur radio
VHF (30-300 MHz)  — FM radio, TV, 4G Band 7
UHF (300MHz-3GHz) — TV, 4G/5G (700MHz-2.6GHz), WiFi, Bluetooth
SHF (3-30 GHz)    — satellite, microwave, 5G mmWave starts here
EHF (30-300 GHz)  — mmWave 5G (28/39 GHz), radar

5G Key Parameters

5G NR peak speed:   20 Gbps DL, 10 Gbps UL
Latency:            < 1ms (URLLC), < 4ms (eMBB)
Connection density: 1 million devices per km²
Frequencies:        FR1 (< 6GHz), FR2 (24-100 GHz mmWave)
Modulation:         Up to 256-QAM
MIMO:               Massive MIMO (64T64R or higher)
Numerology:         μ=0 (15kHz), μ=1 (30kHz), μ=3 (120kHz for mmWave)

E1 / T1 Quick Facts

E1:  32 timeslots × 64kbps = 2.048 Mbps
     30 voice + 1 signaling + 1 framing = 32 total
T1:  24 timeslots × 64kbps = 1.544 Mbps
     24 voice + framing = 25 total
STM-1 = 155.52 Mbps = 63 × E1s

OSI 7 Layers

7 Application   — HTTP, FTP, SMTP, DNS, SIP
6 Presentation  — SSL/TLS, encoding, compression
5 Session       — RPC, NetBIOS, session management
4 Transport     — TCP, UDP, SCTP (segments/datagrams)
3 Network       — IP, ICMP, OSPF, BGP (packets)
2 Data Link     — Ethernet, WiFi, PPP (frames)
1 Physical      — Copper, Fiber, Radio (bits)

Quick Reference — Bsnl Jto Prep

Key Points for Revision

•Review the overview section for core architecture and fundamentals

•Practice commands/configurations from the cheatsheet section

•Use interview Q&A for active recall before exams or interviews

•Cross-reference with related tools in the telecom academy

Practice Approach

1.Read the overview to understand what and why

2.Work through fundamentals for how

3.Attempt hands-on labs or configurations

4.Test yourself with interview questions

5.Keep cheatsheet accessible for quick reference during work

Further Learning

Connect this topic to the broader telecom ecosystem.

Each tool in this academy is designed to work with others —

understanding the integration points is what separates intermediate from senior practitioners.

BSNL JTO/JE Exam Prep — Quick Ref