BSNL JTO flashcards
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32 cards. Read the term and the definition here. The deck at the top of this page is optional.
- Shannon Capacity Formula
- For a channel of bandwidth B hertz with signal-to-noise ratio S/N, maximum error-free data rate is C = B log2(1 + S/N) bit/s. It sets an upper bound, not a guaranteed achieved rate.
- Nyquist Bit Rate
- For a noiseless channel of bandwidth B with M discrete signal levels, the maximum symbol rate is 2B baud and the bit rate is 2B log2(M) bit/s.
- PCM Bit Rate
- Pulse code modulation samples an analog signal at least twice its highest frequency, quantizes each sample into n bits, and outputs fs times n bit/s, such as 64 kbit/s for voice.
- GPON Wavelength Plan
- Gigabit passive optical networks carry downstream traffic at 1490 nm, upstream at 1310 nm, and optional video overlay at 1550 nm, typically splitting one feeder fiber to 32 or 64 users.
- IPv4 Private Address Ranges
- RFC 1918 reserves 10.0.0.0/8, 172.16.0.0/12, and 192.168.0.0/16 for internal use. These addresses are not routed on the public internet and require NAT for external access.
- Usable Hosts Per Subnet
- With h host bits remaining after the prefix, usable addresses equal 2^h minus 2, subtracting the network and broadcast addresses. A /26 leaves 6 bits and 62 usable hosts.
- OSI Layer Functions
- Layer 1 physical, layer 2 data link with MAC, layer 3 network with IP routing, layer 4 transport with TCP and UDP, then session, presentation, and application layers.
- FSPL Formula
- Free-space path loss in decibels equals 32.44 plus 20log10 of distance in kilometers plus 20log10 of frequency in megahertz, giving 6 dB extra loss per doubling.
- Virtual Short in Op-Amps
- With negative feedback and very high open-loop gain, the op-amp drives its inputs to nearly equal voltage, so V+ approximately equals V-. This fails in open-loop or positive-feedback comparator circuits.
- Inverting Amplifier Gain
- An inverting op-amp stage has voltage gain of minus Rf divided by Rin. The input impedance equals Rin and the output is inverted by 180 degrees.
- AM Power Efficiency
- For amplitude modulation with modulation index m, total power is Pc(1 + m squared over 2) and efficiency is m squared over (2 plus m squared), peaking at 33.3 percent when m equals one.
- Carson's Rule
- FM bandwidth is approximately twice the sum of peak frequency deviation and the highest modulating frequency. The modulation index beta equals deviation divided by modulating frequency.
- Aliasing and Anti-Aliasing
- If sampling rate is below twice the highest signal frequency, components above half the sampling rate fold back as false low frequencies. An analog low-pass filter before the sampler prevents this.
- CMOS Dynamic Power
- Complementary MOS draws almost no static current but dissipates dynamic power equal to capacitance times supply voltage squared times switching frequency, so power scales with V squared.
- BJT Active Region
- In the active region the base-emitter junction is forward biased and the base-collector junction is reverse biased. The transistor then behaves as a current amplifier with collector current beta times base current.
- MOSFET Saturation Condition
- A MOSFET operates in saturation when drain-source voltage exceeds gate-source voltage minus threshold voltage. Drain current then follows a square-law dependence on the gate overdrive.
- Sampling Theorem
- A bandlimited signal with highest frequency fmax can be reconstructed exactly if sampled at fs at least 2 fmax. Sampling exactly at that rate requires ideal brick-wall filtering.
- TCP Three-Way Handshake
- A TCP connection opens with SYN from client, SYN-ACK from server, and ACK from client, agreeing on initial sequence numbers before data flows. UDP has no equivalent handshake.
- Well-Known Port Numbers
- Ports 0 to 1023 are well known, including 22 SSH, 25 SMTP, 53 DNS, 80 HTTP, and 443 HTTPS. Ports 1024 to 49151 are registered and 49152 to 65535 are ephemeral.
- Binary Search Complexity
- Binary search halves a sorted array each step, needing at most log base 2 of n comparisons. It requires random access and sorted input, so linked lists are unsuitable.
- Third Normal Form
- A relation is in 3NF when it is in 2NF and no non-key attribute depends transitively on the primary key. This removes redundancy caused by non-key attributes depending on other non-key attributes.
- Deadlock Four Conditions
- Deadlock requires mutual exclusion, hold and wait, no preemption, and circular wait simultaneously. Preventing any single condition, such as ordering resource requests, avoids deadlock.
- Stack vs Queue
- A stack is last-in-first-out with push and pop at one end. A queue is first-in-first-out with insertion at the rear and removal at the front, as used in scheduling buffers.
- ARP and DNS Roles
- ARP maps an IP address to a MAC address inside a local network through broadcast. DNS maps human-readable hostnames to IP addresses using a hierarchical distributed database.
- SQL COMMIT and ROLLBACK
- COMMIT permanently saves a transaction's changes and satisfies durability. ROLLBACK undoes all uncommitted changes, restoring the state at the last commit or savepoint.
- IPv4 TTL Field
- The time-to-live byte in an IPv4 header is decremented by each router. A packet reaching zero is discarded and an ICMP time-exceeded message is returned, preventing infinite loops.
- Train Crossing a Pole
- Time to pass a stationary pole equals train length divided by speed. To pass a platform, use train length plus platform length divided by speed, converting km/h to m/s by 5/18.
- Combined Work Formula
- If A alone takes a days and B alone takes b days, working together they finish in ab divided by (a plus b) days, since their rates add.
- Compound vs Simple Interest
- Compound interest is P(1 + R/100)^T minus P while simple interest is PRT/100. For two years the difference equals P times (R/100) squared.
- Successive Percentage Change
- Two successive changes of a percent then b percent produce a net change of a plus b plus ab/100 percent. A 20 percent rise then 20 percent fall nets a 4 percent decrease.
- Average Shift Rule
- Adding a constant k to every observation raises the mean by k, and multiplying every observation by k multiplies the mean by k. The mean always lies between the smallest and largest values.
- Indian Telecom Regulators
- TRAI regulates tariffs, interconnection, and quality of service, while the Department of Telecom frames licensing and spectrum policy. BSNL is a state-owned operator providing fixed and mobile services.