WBBSE Madhyamik Telecom (Vocational) flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

PCM bit rate

A 4 kHz voice channel sampled at 8000 samples per second and coded with 8 bits per sample gives 64 kbps, the basic DS-0 rate of digital telephony.

Simplex transmission

One-way communication only, such as radio or television broadcast, where the receiver can never send data back to the transmitter.

Decibel

A logarithmic ratio of two power levels, dB = 10 log10(P2/P1), used to express gain, loss and signal-to-noise ratio in telecom links.

Shannon capacity formula

The maximum error-free data rate C = B log2(1 + S/N) bits per second, where B is bandwidth in hertz and S/N the linear signal-to-noise ratio.

Total internal reflection

Light striking the core-cladding boundary above the critical angle is reflected back into the core, the effect that guides the signal along an optical fibre.

STM-1 rate

The first level of the SDH hierarchy, carrying 155.52 Mbps, which equals 63 E1 tributaries of 2.048 Mbps or three STM-0 signals.

Circuit switching

A connection-oriented technique that reserves a dedicated end-to-end path for the whole call, as in the PSTN, giving fixed delay but wasting capacity when idle.

Erlang

The unit of telephone traffic; one Erlang equals one circuit occupied continuously for one hour, used with grade of service to size trunk groups.

Reuse factor

In cellular planning, the fraction 1/N of total spectrum available to each cell in a cluster of N cells, where N = i² + ij + j².

Handoff

The process by which an ongoing call is transferred from one base station to another as the subscriber moves between cells, without dropping the connection.

HLR and VLR

The Home Location Register stores a subscriber's permanent profile and current location, while the Visitor Location Register holds temporary data of roamers served by that MSC.

GSM TDMA frame

A GSM carrier occupies 200 kHz and its 4.615 ms frame carries 8 time slots, letting up to eight full-rate speech users share one frequency simultaneously.

Private IPv4 ranges

The non-routable blocks 10.0.0.0/8, 172.16.0.0/12 and 192.168.0.0/16 used inside local networks behind NAT and never forwarded on the public internet.

DNS

The Domain Name System is the distributed hierarchy that resolves names such as example.com into IP addresses, normally using UDP port 53.

TCP versus UDP

TCP is connection-oriented with handshake, sequencing and retransmission; UDP is connectionless with no delivery guarantee and suits live voice, video and short queries.

ADSL

Asymmetric Digital Subscriber Line runs over the existing copper pair, providing higher downstream than upstream speed while sharing the line with analogue telephone service.

T568B pinout order

RJ-45 wiring order: white-orange, orange, white-green, blue, white-blue, green, white-brown, brown. Identical order at both ends makes a straight-through patch lead.

Fusion splicing

Joining two optical fibres by melting their cleaved ends with an electric arc; typical splice loss is 0.05 to 0.1 dB, the lowest-loss permanent joint.

VSWR

Voltage Standing Wave Ratio measures impedance mismatch between transmitter and antenna feed; 1:1 is perfect and a reading above about 1.5:1 indicates a fault.

MTTR

Mean Time To Repair is the average time needed to restore a failed system, and availability equals MTBF divided by the sum of MTBF and MTTR.

ARPU

Average Revenue Per User is total revenue divided by the average number of subscribers in the period, a key profitability metric for telecom operators.

Mobile number portability

A facility letting a subscriber keep the same mobile number when changing operator or service area, coordinated nationally through clearing-house validation.

SLA

A Service Level Agreement is a contract clause defining measurable targets such as uptime, latency and fault restoration time, with penalties if targets are missed.

MOS score

Mean Opinion Score rates voice quality subjectively from 1 (bad) to 5 (excellent); 4 or above is toll quality and PESQ gives an automated estimate.

Full body harness

Personal fall-arrest equipment with chest and leg straps plus a lanyard anchored above the worker; mandatory for work at height with 100% tie-off while climbing.

Lockout tagout

A procedure for isolating and padlocking an energy source and attaching a warning tag before maintenance, so the equipment cannot be re-energised accidentally.

Laser eye hazard

Infrared light at 1310 and 1550 nm from an open fibre is invisible and can damage the retina; never look into a fibre end, use an optical power meter.

CO2 extinguisher use

Carbon dioxide extinguishers suit live electrical and electronic fires because they leave no residue; operate them with PASS: Pull, Aim, Squeeze, Sweep.

STAR interview method

Answering behavioural questions by describing the Situation, Task, Action and Result, keeping the reply structured and ending with a measurable outcome.

Break-even point

The sales volume at which total revenue equals total cost, calculated as fixed cost divided by unit price minus unit variable cost.

Udyam registration

India's free online registration for micro, small and medium enterprises, based on Aadhaar and PAN, required for MSME benefits and priority lending.

Active listening

Fully concentrating on the speaker, not interrupting, and paraphrasing or summarising what was said to confirm understanding before replying.