Notes, summaries, assignments, exams, and exercises for Electronics for Vocational training

Pulse Code Modulation (PCM) Fundamentals

1. Sampling Process

Samples are taken for the analog signal, measuring its amplitude (voltage). The process involves the following steps:

1. The telephone signal has a voice frequency range of 300–3400 Hz. It passes through a low-pass filter, considering the signal from 0 to 4 kHz.
2. A sample is taken instantaneously, and the amplitude value is retained for measurement.
3. According to Nyquist's theorem, we need a sampling frequency ($f_s$) twice the maximum signal frequency ($f_s \ge 2f_{max}$). For a 4 kHz signal, this results in a sample every 125 $\mu$s (microseconds), corresponding to $f_s = 8,000$ samples/second.
4. This process yields a train of Pulse Amplitude Modulated (PAM) pulses.

2. Quantization and Companding

The...

Understanding Electric Current and Circuits

Electric current is the passage of electrical charge through a conductor. This occurs when there is an imbalance of charge between two points of the conductor.

An electric circuit is a set of elements connected together through which electric current flows. For current to flow, the circuit must be closed.

Components of an Electric Circuit

• Generator: Builds and maintains the voltage needed to produce the current.
• Conductors: Pathways through which the electric current flows, usually made of copper or aluminum.
• Receivers: Elements that transform electrical energy into other forms of energy.
• Switching and Control Elements: Direct the flow of electrical current.
• Protection Elements: Protect individuals and the

Electrical Encoding Schemes

There are two main types of encoding schemes: single-core and multi-threaded functional circuit diagrams.

Electrical Magnitudes and Measurement

Here's a table summarizing common electrical magnitudes, their units, and the instruments used for their measurement:

Multimeter

A multimeter is a versatile instrument used to measure various electrical quantities.

Absolute Error

Absolute error refers to the difference between the value read on an instrument and the actual value.

Common Electrical Issues

Surge

A surge is an excess of voltage affecting the electrical grid. Surges...

Modulation Techniques in Broadcast Channels

Television transmission utilizes various combinations of modulation techniques, including:

• Amplitude Modulation (AM) combined with Vestigial Side Band (VSB) and Double Sideband Modulation (DSB)
• Quadrature Amplitude Modulation (QAM)
• Frequency Modulation (FM)
• Phase Shift Keying (PSK)
• Coded Orthogonal Frequency-Division Multiplexing (COFDM) for digital transmission

Pre-emphasis: Usage and Purpose

Where and for what purpose is pre-emphasis used in modulation?

In the path of the sound signal, and prior to modulation, a high-pass filter must be applied. This process, known as pre-emphasis, raises the level of high audio frequency components to significantly improve the signal-to-noise ratio (SNR) of the transmission....

Hydrants and Equipment

Hydrants are equipped with essential firefighting tools, primarily hoses. These hoses connect to a pressurized water network, providing a constant water supply for initial fire suppression. Key components include:

1. Hose
2. Valve Connection
3. Support
4. Nozzle Connector (connects the hose to the nozzle tip)
5. Nozzle (directs, regulates, and controls water flow)

Hydrants: External Fire Prevention

Hydrants form part of the fixed fire prevention system. They are located outside buildings and connect to the water supply network through independent conduits. Hydrants are exclusively for firefighter use.

Fire in Electrical Installations

Source of Electrical Fires: Overcharge, voltage spikes, short circuits, and defective equipment.

Causes: Poorly...

Derivades

Limits

Verb "To Be" Forms

Am, are, is

Present Simple

Infinitive or add 's' / Use don't for negatives

Past Simple

Add -ed (or second column for irregular verbs) / S + didn't + infinitive / Did + subject + infinitive

Used for actions at a specific time, consecutive actions in the past, a short action interrupting a longer one, or describing past states.

Past Tense of "To Be"

Was/were

Passive Voice

Subject + to be + past participle (-ed or third column) + by + agent

• Present Simple: am/are/is + past participle
• Past Simple: was/were + past participle
• Present Continuous: am/are/is being + past participle
• Past Continuous: was/were being + past participle
• Present Perfect: have/has + been + past participle
• Modal: modal + be + past participle
• Future Simple: will be + past participle

Question

Understanding Electricity Billing

Let's break down the components of your electricity bill:

• Power Term (T. potencia): A fixed amount paid in billing, determined by the contracted power.
• Energy Term (T. energia): The amount paid for the actual energy consumed.

Types of Electricity Rates

• Last Resort Rate (TUR): Replaces the former "integral rate," set by the government. It features a single price for all users. Available for those with contracted power less than 10kW.
• Toll-Free Rate: You can negotiate different conditions than the TUR with a marketer.
• Access Fee: Covers the cost of using the distribution network to bring electricity to your home. Not applicable if you have the TUR.
• Social Bond: A tariff designed to protect households with fewer resources.

First Generation Computers: The Vacuum Tube Era

The first generation of computers was based on vacuum tubes—electronic components similar to light bulbs. These tubes could be held in two different states, conducting or non-conducting, which allowed for the construction of digital systems based on binary logic.

Key Computers of the First Generation

• ENIAC (1947): Consisting of 18,000 valves and 7,500 resistors, it could perform decimal addition, subtraction, multiplication, and division. It filled the basement of the University of Pennsylvania, consumed 100 kW of power, and reached a processing speed of 5,000 additions per second.
• EDVAC (1949): The first computer based on the philosophy of John von Neumann, featuring programs stored in memory alongside

Channel Signaling: Types and Performance

Channel-Associated Signaling

Channel-associated signaling transmits signals needed to manage and control a particular channel conversation along with the channel itself. Traditionally, the signals corresponding to a circuit are transmitted by the circuit itself.

Common Channel Signaling

The introduction of stored program control (SPC) leads to a novel method of marking. The control unit can send signaling channel signals for all circuits which are in conversation on a particular route. This method is called common channel signaling.

Signaling System Performance

When establishing a signaling system, it's necessary to determine the role the intermediate centrals will play in the performance of their control...