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Slave clock

Slave clock is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Slave clock rather than just read about it. In short: In telecommunication and horology, a slave clock is a clock that depends on another clock, the master clock. Modern clocks are synchronized through the Internet or by radio time signals, to Coordinated Universal Time.

Slave clock — main illustration
Slave clock — illustration

Key takeaways

  • Slave clock belongs to science; place it in that map before memorising details.
  • Learn the definition first, then one example that makes the definition concrete.
  • Connect Slave clock to a quantity you can measure, compute or draw — that is where exam questions come from.
  • Reproduce the core statement of Slave clock from memory before moving on to harder problems.

Reference excerpt

In telecommunication and horology, a slave clock is a clock that depends on another clock, the master clock. Modern clocks are synchronized through the Internet or by radio time signals, to Coordinated Universal Time. UTC is based on a network of atomic clocks in many countries. For scientific purposes, precision clocks can be synchronized to within nanoseconds by dedicated satellite channels. Slave clock synchronization is usually achieved by phase-locking the slave clock signal to a signal received from the master clock. To adjust for the transit time of the signal from the master clock to the slave clock, the phase of the slave clocks are adjusted so that both clocks are in phase. Thus, the time markers of both clocks, at the output of the clocks, occur simultaneously. The predecessors of atomic clocks, computer clocks, and digital clocks, these electric clocks (or pneumatic clocks) were synchronized by an electrical pulse, wired to their master clock in the same facility. (In the case of pneumatic clocks, pneumatic tubing was used instead of electrical wiring.) Hence the terms "master" and "slave." From the late 19th to the mid 20th centuries, electrical master/slave clock systems were installed, all clocks in a building or facility synchronized through electric wires to a central master clock. Slave clocks either kept time by themselves, and were periodically corrected by the master clock, or required impulses from the master clock. Many slave clocks of these types were in operation, most commonly in schools, offices, military bases, hospitals, railway networks, telephone exchanges and factories the world over. School bells of elementary schools, high schools, and others were able to be synchronized across an entire campus, connected to the system. In schools, the master clock was in the principal's office, with slave units in classrooms which were in other buildings on campus. In factories, a system with a bell or horn could signal the end of a shift, lunchtime or break time. Very few relics of this electrical, analogue system operate in the 21st century. Most 21st century systems of the type are digital.

Pictures Mechanical slave clocks from the 1950s and 1960s era.

See also Clock network

References

External links All about electric master and slave clocks British GPO Clock Systems

Illustrations

Slave clock: Diagram of electric time system used around 1910 to keep time in factories, schools, and other large institutions. The master clock (bottom center), controlled by a temperature-compensated mercury pendulum, is wired to slave clocks throughout the building. In addition to wall clocks, it also controls time stamps that are used to stamp documents with the time, and a turret clock used in a clock tower. The "program clock" is a timer that can be programmed with punched paper tape to ring bells or turn machines on and off at preprogrammed times.
Diagram of electric time system used around 1910 to keep time in factories, schools, and other large institutions. The master clock (bottom center), controlled by a temperature-compensated mercury pendulum, is wired to slave clocks throughout the building. In addition to wall clocks, it also controls time stamps that are used to stamp documents with the time, and a turret clock used in a clock tower. The "program clock" is a timer that can be programmed with punched paper tape to ring bells or turn machines on and off at preprogrammed times.
Slave clock illustration
Slave clock illustration
Slave clock illustration
Slave clock illustration

Worked examples

Example 1 — a first encounter with Slave clock

Start with the simplest possible case. Write down what Slave clock claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Slave clock before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Slave clock ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Slave clock

In research
Slave clock appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry
Engineering practice reuses Slave clock in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom
Slave clock is common in secondary-school and first-year university syllabi. It links to neighbouring topics Clocks, Digital electronics, Telecommunications equipment, so understanding it makes those chapters shorter.
In everyday life
Look for Slave clock outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Slave clock in 20 minutes

  1. Read the reference excerpt below once, without taking notes.
  2. Close the page and write down what Slave clock means in your own words.
  3. Compare your version with the excerpt and mark what you missed.
  4. Work through the three examples above with pen and paper.
  5. Explain Slave clock out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Slave clock in simple terms?

In telecommunication and horology, a slave clock is a clock that depends on another clock, the master clock. Modern clocks are synchronized through the Internet or by radio time signals, to Coordinated Universal Time.

Why does Slave clock matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Slave clock?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Slave clock.

Tags

  • Clocks
  • Digital electronics
  • Telecommunications equipment

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