Cellular Phone Technology and Network Fundamentals

Cellular phones get their name from the cellular system architecture where geographic areas are divided into hexagonal 'cells' each served by a base station. As a user moves between cells, the call is handed off to the next cell's base station, enabling continuous communication. This cellular division allows for efficient frequency reuse and expanded network capacity.

Full-duplex communication allows simultaneous two-way transmission and reception, which is what enables cell phone users to talk and listen at the same time. Half-duplex requires taking turns (like walkie-talkies), while 'multiple-duplex' is not a standard communication term. This simultaneous communication capability is a key difference between cell phones and traditional radio systems like CB radios.

Each cell phone base station typically serves a range of approximately 10 square miles or 26 square kilometers in urban and suburban areas. This range can vary based on terrain, population density, and technology, with rural areas having larger cells and dense urban areas having smaller cells with more base stations to handle capacity.

The Mobile Telephone Switching Office (MTSO) manages the handoff process between cell towers as you move. It monitors your signal strength and coordinates switching your call to a new tower when necessary, which involves changing frequencies. This seamless coordination allows continuous conversations while moving between cells.

Cell phones identify roaming by comparing the System ID (SID) of the current tower with their home SID stored in the MTSO database. When these IDs don't match, the phone recognizes it's operating outside its home service area and roaming charges may apply.

Digital phones convert voice signals into binary code (1s and 0s) using compression algorithms like vocoders. This digital compression allows multiple calls to be transmitted simultaneously on the same frequency through techniques like TDMA or CDMA, unlike analog phones that require dedicated frequencies.

Cell phone cloning is a fraud technique where criminals copy the electronic serial number (ESN) and mobile identification number (MIN) from a legitimate phone. These stolen identifiers are then programmed into another phone to make calls that are billed to the victim's account.

Cell phones use low-power signals because cell towers are positioned close together (signals don't need to travel far), and this design conserves battery life since transmitting weaker signals consumes less power. High-power transmission would quickly drain the battery and cause interference between nearby cells.

A locked phone is restricted by software to work only with the specific carrier that sold it, typically through a SIM lock or network lock. This prevents the phone from accepting SIM cards from other providers, ensuring the carrier recovers their subsidy on the device.

Hyponatremia is a condition where blood sodium levels are abnormally low. Hypokalemia involves potassium deficiency. Anaemia relates to red blood cells or iron deficiency. 'Hypocalmia' appears to be a misspelling of hypocalcemia (calcium deficiency).

Rickets develops in children due to insufficient vitamin D, calcium, and phosphate, causing soft and weak bones. Measles is a viral infection. Rabies is a viral disease from animal bites. Chicken pox is a viral infection from the varicella-zoster virus.

Pellagra is the classic disease of niacin (vitamin B3) deficiency, characterized by the '3 Ds': diarrhea, dermatitis, and dementia. Ariboflavinosis is caused by riboflavin (B2) deficiency, while haemophilia is a genetic bleeding disorder unrelated to vitamin deficiencies. Pneumonia is an infectious disease.

Colour blindness is the correct condition where a person has difficulty distinguishing between certain colors, most commonly red and green (though blue-yellow color blindness exists). Blindness means complete inability to see, while X and Y chromosomes are genetic structures, not diseases.

Iodine deficiency causes goitre, a condition characterized by abnormal enlargement of the thyroid gland in the neck. The thyroid requires iodine to produce hormones, and when iodine is insufficient, the gland enlarges to compensate. Thyroid is the gland itself (not the disease), Pellagra is caused by niacin (B3) deficiency, making Goitre the correct answer.

Vitamin A refers to a group of compounds called retinoids, including retinol, retinal, and retinoic acid. Vitamin Ace is not a valid chemical name. Thiamine is Vitamin B1. Retinoids is the correct chemical class for Vitamin A compounds.

Vitamin B1 is called thiamine. It's a water-soluble B-complex vitamin essential for carbohydrate metabolism. Riboflavin is Vitamin B2, not B1.

Vitamin B2 is chemically known as riboflavin. It's essential for energy production and cellular function. Biotin is Vitamin B7, and pellagra is a disease caused by Vitamin B3 deficiency.

Vitamin B3 is known as niacin or nicotinic acid. It's crucial for DNA repair and cholesterol regulation. Pyridoxal is Vitamin B6, and ariboflavinosis is a B2 deficiency disease.