AGL Series Circuit: Primary & Secondary Circuits Notes

THE CORE SPLIT: PRIMARY AND SECONDARY

A conventional AGL system rests on a clear separation between the primary series circuit and the secondary circuit. The primary carries the controlled current from the CCR through the primary windings of the isolation transformers. The secondary connects each isolation transformer to one individual fitting.

This distinction underpins design, transformer, cable and connector selection, fault finding, insulation testing, commissioning, photometric troubleshooting and maintenance. FAA specifications treat the series-circuit equipment separately: L-824 underground cable, L-823 connectors, L-830/L-831 isolation transformers and CCRs.

The most important difference

PRIMARY = COMMON SERIES CIRCUIT
SECONDARY = INDIVIDUAL FIXTURE CIRCUIT
This one idea explains a large part of AGL electrical troubleshooting

AGL controlCCRPrimary series circuitIsolation transformerSecondary circuitFixture

THE PRIMARY CIRCUIT

The primary circuit is the main series circuit supplied by the CCR. It consists of the CCR, primary series cable, isolation-transformer primary windings, primary connectors, cable joints and accessories, and the return cable to the CCR. It is a series circuit, so the same controlled current flows through the whole path.

CCR
 │
 PRIMARY SERIES CABLE
 │
[IT1] ── cable ── [IT2] ── cable ── [IT3] ── ... ── RETURN TO CCR

IT = isolation transformer (primary winding in the series path)

The transformer is not a normal parallel load across the CCR output. Its primary winding is part of the series path (H1 in, H2 out).

Primary component	Role
CCR	Supplies regulated series current
Primary cable	Carries the series current around the airfield circuit
Primary connector	Joins cable to transformer and other cable sections
Transformer primary	Forms part of the series circuit
Joints / accessories	Maintain continuity of the underground circuit
Return cable	Completes the loop back to the CCR

THE SECONDARY CIRCUIT

The secondary circuit is the individual circuit between one isolation transformer and its fitting. Unlike the common primary loop, it is generally an individual load circuit: Transformer 1 → Fixture 1, Transformer 2 → Fixture 2, and so on. This gives electrical isolation between the individual loads.

Transformer secondarySecondary cableSecondary connectorAGL fixture

Secondary component	Role
Transformer secondary	Produces the required secondary output
Secondary cable	Carries power from transformer to fitting
Secondary connector	Provides the field connection
AGL fixture	Converts electrical energy into the required visual output

This is why the failure of one fixture's secondary circuit does not necessarily interrupt the complete primary series loop.

PRIMARY VS SECONDARY AT A GLANCE

Parameter	Primary circuit	Secondary circuit
Main purpose	Complete AGL series power circuit	Individual fitting supply
Source	CCR	Isolation transformer
Configuration	Series	Individual branch / load circuit
Main current	CCR-controlled	Determined by transformer and load
Main cable	AGL primary cable	Secondary cable
Transformer role	Primary winding is in the circuit	Secondary winding supplies the load
Typical number	One complete series loop	One per individual fitting
Fault impact	Can affect many fittings	Usually affects one fitting
Main concern	Circuit continuity and insulation	Individual fitting supply
Connector	Primary AGL connector	Secondary AGL connector

Cable comparison

Primary cable	Secondary cable
Part of the main series loop	Individual fixture connection
Connects CCR and transformer primaries	Connects transformer to fixture
Carries regulated series current	Carries individual load current
Higher insulation demands (typically 5,000 V-rated L-824)	Lower voltage than primary in typical systems (typically 600 V-rated)
Long underground routes common	Usually relatively short
Fault can affect several fittings	Usually affects one fitting

Actual ratings must always come from the approved system design.

WHY AGL USES A SERIES CIRCUIT

A series system lets many field fittings share a common circuit supplied by a CCR, which controls the current through the loop. Advantages include controlled current, defined intensity steps, long-distance distribution, individual fixture isolation through transformers, and less dependence on individual parallel supply circuits.

Series AGL vs building (parallel) lighting

	Building lighting	AGL series circuit
Arrangement	Supply feeds each light in parallel	CCR → transformer → cable → transformer → … → return
Common quantity	Voltage is common across branches	Circuit current is controlled through the loop

Because the same current flows through every light, brightness stays uniform whatever the cable length or the number of lights. Confusing series and parallel affects cable sizing, transformer design, fault behaviour, protection, control and troubleshooting.

AC 150/5345-10H specifies CCRs and defines their regulated-current characteristics; see Note 07: Constant Current Regulators.

PRIMARY CURRENT, VOLTAGE AND IMPEDANCE

The CCR controls current. Typical primary currents are 6.6 A and 20 A, set by the CCR and the equipment specification (AC 150/5345-10H: Class 1 about 6.6 A, Class 2 about 20 A).

Primary current affects transformer operation, cable losses, circuit voltage, CCR loading, transformer and connector selection, and light intensity. A 6.6 A circuit needs transformers with a 6.6 A primary rating; a 20 A-primary unit cannot be substituted just because the wattage matches.

V ≈ I × Z          V = circuit voltage · I = regulated current · Z = effective impedance
Vtotal ≈ Σ voltage drops around the series circuit
Ztotal = Ztransformers + Zcable + Zconnections + other impedance

As circuit length, transformer loading and impedance change, the voltage needed to hold the selected current changes. The CCR must drive current through cable resistance, transformer impedance and connector/contact resistance, so it may develop substantial voltage.

5 kV is a rating, not an operating voltage. The FAA L-830/L-831 transformer specification gives a 5,000 V primary voltage rating. Do not read this as every AGL series circuit running continuously at 5 kV.

CABLE: RESISTANCE, LENGTH AND SELECTION

Primary cable is one of the most critical components. AC 150/5345-7F is the FAA specification for L-824 underground electrical cable for airport lighting circuits.

Vdrop = I × R        Ploss = I²R        Length ↑ → Resistance ↑ → Voltage drop ↑

For a fixed current, higher resistance means higher I²R loss, so a small resistance increase can produce a significant loss increase. The total route length must be accounted for, which is one reason CCR capacity cannot be set from the number of lamps. The same principle applies to the secondary cable: a long or undersized one gives reduced fixture voltage and output, heating and poor performance.

Select primary cable by

Operating circuit and current
Voltage / insulation requirement
Cable length and conductor size
Resistance
Installation environment
Connector compatibility
Applicable standard and project specification

Select secondary cable by

Transformer secondary current
Fixture requirements
Cable length and insulation
Temperature
Mechanical protection
Connector compatibility
Installation conditions

CONNECTORS AND CONTACT RESISTANCE

AC 150/5345-26E covers L-823 plug and receptacle cable connectors used with underground power cables, isolation-transformer leads and light-fixture leads. A connector must provide electrical continuity, insulation, environmental protection, mechanical integrity, correct polarity/configuration and reliable long-term contact. A primary connector problem can become a series-circuit fault.

Connector resistance risesVoltage drop risesI²R loss risesConnector heating

The connector configuration must match the approved equipment: primary cable → L-823 connector → transformer primary, and transformer secondary → L-823-compatible connection → secondary cable → fixture.

THE TRANSFORMER: THE INTERFACE

Primary and secondary windings are electrically isolated and magnetically coupled. AC 150/5345-47C covers series-to-series isolation transformers. Ideal relationships are Vp / Vs = Np / Ns and Vp × Ip ≈ Vs × Is, but real AGL transformers must be taken from their specified characteristics, including losses.

Primary and secondary current are not automatically equal

Primary	Secondary	Note
6.6 A	6.6 A	Common arrangement
20 A	6.6 A	Fundamentally different from 6.6 / 6.6 A
6.6 A	20 A	Specified types exist
20 A	20 A	Specified types exist

Confirm the exact primary/secondary combinations and wattage sizes in the current AC 150/5345-47C before selecting a transformer.

200 W, 6.6 A / 6.6 A

6.6 A primary series circuit, 200 W transformer, 6.6 A secondary. This does not mean primary and secondary voltages are identical; current may match nominally while voltage differs.

200 W, 20 A / 6.6 A

20 A primary, 6.6 A secondary. The FAA specification has separate types for these two 200 W arrangements, so the circuit current must be confirmed.

Frequency must suit the CCR, transformer, fixture and project electrical system: L-830 = 60 Hz, L-831 = 50 Hz. Details are in Note 08: AGL Isolating Transformers.

Fixture loadPrimary circuit (6.6 A or 20 A)Secondary requirementFrequencyTransformerCableConnectorsStandards

ONE LIGHT OUT VS PRIMARY OPEN

One light fails

Say Fixture 3. Possible locations: transformer 3, secondary connector, secondary cable, fixture 3. The complete primary circuit may remain operational. This is one of the most important troubleshooting concepts in AGL.

Primary cable breaks (open circuit)

The series loop is interrupted and current stops everywhere in that loop, so every light on that circuit goes out and the CCR will normally trip on open circuit. There is no "downstream only" effect in a single series loop. The break is then found by splitting the circuit and testing section by section.

CCR → IT-1 → IT-2 ──X── IT-3 → IT-4      (open circuit: loop interrupted, ALL lights on the circuit go out)

Open secondary loads

The transformer primary stays in the series loop even when its secondary load is open. However, enough open or faulted secondary loads can change overall circuit loading and, depending on CCR design, affect CCR operation.

Why primary faults are more serious

Fault	Likely reach
Primary open circuit	The whole circuit goes dark
Primary short or double earth fault across a section	The lights in the bypassed section go dark; the rest stay lit because the CCR holds the current
One secondary fault	Usually one fitting

Why circuits are interleaved: because one open primary loop darkens every light on it, lights on a runway or taxiway are normally shared across more than one circuit in line with the project design, so a single circuit failure does not remove all the lights in an area.

PRIMARY CIRCUIT LOAD AND DESIGN

Primary load depends on more than the number of lamps: transformer rating, fixture load, transformer and cable losses, number of fittings, open secondary loads, circuit impedance and operating current.

Rule

AGL circuit design = complete electrical circuit calculation
Not number of lights × wattage

Primary circuit design sequence

Lighting functionNumber of fixturesFixture wattagesTransformer typesPrimary currentCircuit lengthCable characteristicsImpedance / loadSelect CCRCheck transformers and connectorsTest

Secondary circuit design sequence

FixtureWattageTransformerSecondary currentSecondary cableConnectorCable lengthVoltage drop / performanceFixture operationPhotometry

INSULATION, MOISTURE AND FAULT TYPES

A primary circuit can be electrically continuous and still be defective: continuity good, insulation bad, caused by moisture, cable damage, a poor joint, transformer insulation failure or connector contamination. Continuity testing alone never proves a healthy primary circuit.

The insulation system includes cable, transformer, connector and joint insulation; a defect in any one can affect the circuit. Underground and outdoor operation exposes it to moisture, which reduces insulation resistance and causes leakage current, corrosion, tracking, connector failure and transformer faults. That is why specialised AGL cable, connectors and sealed transformers are used (L-824, L-823).

Primary cable fault types

Open circuit: broken conductor or joint
Short circuit: unwanted low-resistance connection
Earth fault: insulation failure leaking to ground
High-resistance joint: voltage drop and heating
Intermittent fault: changes with movement, temperature or moisture

Secondary circuit fault types

Open cable
Shorted cable
Damaged connector
Fixture failure and driver failure
Transformer secondary failure
Water ingress

Primary short circuit and earth faults. A CCR regulates current, so a short across part of the loop does not normally raise the current: the lights in the bypassed section go dark and the CCR may operate its protection. A series circuit is floating (not earthed), so a single earth fault usually does not stop the circuit, but a second earth fault at another point can bypass part of the loop and stress the insulation. Protection should respond according to the approved system design.

CABLE JOINTS

Joints are critical points in an underground AGL circuit. A poor joint causes high resistance, moisture ingress, insulation failure, intermittent operation or series-circuit interruption.

Joint inspection

Correct joint kit
Correct cable preparation
Proper conductor connection
Adequate insulation
Water sealing
Mechanical protection
Correct identification
Test result recorded

CONTROL, BRIGHTNESS AND PHOTOMETRY

The control system does not normally control each secondary fitting independently. The CCR is the key interface between control and the field series circuit.

ATC / control roomALCMS / control systemCCRPrimary series circuitTransformersFixtures

The CCR changes the primary current. A lower step gives lower primary current and lower fixture output; a higher step does the reverse. Actual brightness-current values depend on the CCR classification and approved system.

CCR currentTransformerSecondary supplyFixtureOptical outputPhotometry

An electrical problem can therefore become a photometric one: incorrect current → incorrect fixture output → photometric deviation.

LED fixtures. LED fittings have electronic drivers. Verify secondary current and voltage, transformer, connector, driver characteristics, CCR compatibility and manufacturer requirements. Do not assume an LED fixture can replace any older fitting on the existing transformer.

COMMISSIONING

Primary circuit, before energisation

Visual: cable installation, joints, transformer connections, connectors, labels, equipment condition
Electrical: continuity, insulation, earthing/bonding where applicable, correct circuit identification
CCR: correct current, brightness steps, output, monitoring
Field: transformers, fixtures, secondary circuits, photometric performance where required

Secondary circuit, each fitting

Correct connection and fixture
Correct orientation
Correct operation and intensity
No abnormal heating
No visible damage

TESTING AND SAFETY

Primary circuit test sequence

Isolate the system safely.
Identify the circuit.
Verify the cable and transformer arrangement.
Continuity test the primary loop and each secondary path.
Insulation test the primary to earth, with the CCR and any sensitive equipment disconnected from the circuit first.
Check any fault condition.
Reconnect equipment as approved.
Energise and verify the CCR.
Verify field operation.

Continuity checks that the path is complete (CCR output → cable → transformer primaries → return, or transformer secondary → cable → connector → fixture); an open circuit can interrupt it or leave a fitting OFF. Insulation testing covers primary to ground, cable, transformer, connector and joint insulation, and the secondary cable, transformer secondary, fixture and connector condition. Test voltages and acceptance criteria must come from the applicable standard, approved project method statement and manufacturer instruction.

Protect connected electronics. Sensitive electronic or LED equipment must not be subjected to an insulation test unless the approved procedure specifically allows it.

Primary circuits can involve hazardous voltages. De-energise → Isolate → Lockout/Tagout → Verify absence of voltage → Discharge/secure as required → Test → Work. Never assume switching the CCR OFF alone has made the circuit safe. The secondary side is usually lower voltage but must be treated as live until verified otherwise. Follow the airport electrical safety procedure.

For the full commissioning and test-record workflow see Note 14: AGL Testing & Commissioning; for the electrical chain see Note 05.

FAULT-FINDING

Field rule

ALL lights on the circuit off: Power → Control → CCR (and its protection) → open primary loop
MANY lights off but others still lit: the loop is intact, so look for a shorted or bypassed primary section or a shared cause (for example water in a pit or junction)
ONE light off: Secondary circuit / transformer / fixture (start locally)

Many lights OFF (others lit)

Identify affected sectionPrimary cable in that sectionJoints and connectorsInsulation testTransformersIndividual secondaries

One light OFF

FixtureFixture connectorSecondary cableTransformer secondaryTransformerPrimary connection

Starting with the most localised likely fault saves time.

Problem	First investigation
Entire circuit OFF	CCR / input / control / open primary loop
Many lights OFF, others lit	Shorted or bypassed primary section, or a shared cause
One light OFF	Fixture / secondary
CCR trips	Primary circuit / fault / protection
Low fixture output	Secondary / transformer / fixture
Low insulation	Cable / joint / transformer / moisture
Intermittent light	Connector / cable / fixture
Connector heating	Contact resistance / poor connection
Abnormal CCR voltage	Circuit impedance / loading
Several adjacent lights OFF	Shorted or bypassed primary cable section, or a common pit/junction fault

Worked examples

25 of 80 taxiway fittings OFF, the rest lit

The loop is still continuous, or the other 55 would be dark too. Suspect a common cause first: a shorted or bypassed primary section, a double earth fault, or water in a shared pit or junction. It is unlikely that 25 unrelated fixtures failed together.

1 centreline light OFF, neighbours ON

Investigate the fixture, secondary connector, secondary cable and isolation transformer before assuming a CCR failure.

COMMON MISTAKES

Treating the circuit as parallel

Series-circuit AGL uses a different architecture.

Choosing a transformer by wattage only

Primary current and frequency are equally important.

Ignoring cable length

Cable resistance affects circuit voltage and losses.

Ignoring connector resistance

A poor connector can become a significant fault.

Testing only continuity

A circuit can have continuity and poor insulation.

Assuming one light failure means CCR failure

Start with the individual secondary circuit.

Secondary: wrong transformer, connector or cable

Also ignoring LED-driver requirements.

Insulation-testing connected electronics

Check the approved procedure first.

Selection checklists

Primary circuit

CCR: output current, steps, capacity, monitoring, input supply
Cable: type, conductor size, insulation rating, total length, route, jointing method
Transformers: quantity, wattage, primary and secondary current, frequency, type
Connectors: primary connector, cable size, transformer lead, environmental protection
Testing: continuity, insulation, circuit identification, CCR output, functional test

Each secondary (fitting)

Correct transformer and secondary current
Correct secondary cable, length and connector
Correct fixture
Polarity / orientation where applicable
Sealing and mechanical protection
Functional test completed

Quick Revision

QUICK REVISION

Remember

PRIMARY = common series circuit · SECONDARY = individual fixture circuit
CCR controls primary current · transformer isolates and transfers power · fixture produces light
Primary: CCR → Series current → Primary cable → Transformer primary → Return
Secondary: Transformer secondary → Secondary cable → Connector → Fixture
Many lights off: go upstream · one light off: go local
Vdrop = I × R · Ploss = I²R · V ≈ I × Z

                 AGL SYSTEM
                    │
                   CCR
                    │
          PRIMARY SERIES CIRCUIT
         ┌──────────┼──────────┐
        IT1        IT2        IT3
         │          │          │
     Secondary  Secondary  Secondary
         │          │          │
      Fixture    Fixture    Fixture

Keyword Reference

AGL SERIES CIRCUIT: KEY TOPICS

AGL series circuit working principle

In an AGL series circuit the CCR drives one controlled current through the primary cable and the primary windings of every isolation transformer in the loop. Each transformer passes power to its own light, so every light sees the same current whatever the circuit length. Brightness changes by changing that current.

AGL series circuit types

AGL series circuits are grouped by the lights they feed, for example runway edge, centreline, threshold, taxiway, approach and sign circuits. They may differ in current rating, number of brightness steps and whether they are a single loop or a split system.

AGL series circuit functions

The functions of an AGL series circuit are to deliver constant current to many lights, isolate each light from the primary, allow brightness control and keep working when one light fails, as the transformer secondary opens without breaking the loop.

AGL series circuit components

The main components are the CCR, the primary cable, isolation transformers, connectors and joints, the fixtures and the earthing system. The control and monitoring system switches the circuit and reports its status.

AGL series circuit requirements

Requirements for an AGL series circuit come from the standards and project specification: correct current, reliable insulation, suitable cables and connectors, protection, earthing, monitoring and layout that allows the airfield to operate safely when part of a circuit fails.

AGL series circuit design

Designing an AGL series circuit means dividing the lights into circuits, finding the load and cable resistance, and selecting the CCR size and the cable. Circuits are usually arranged so a single failure does not remove too many lights from one area.

AGL series circuit installation

Installing an AGL series circuit includes laying and joining primary cable, fitting transformers and connectors, connecting the CCR and earthing the system. Joints and connectors need particular care, because they are common points of failure.

AGL series circuit maintenance

Maintenance of an AGL series circuit includes periodic insulation and resistance checks, inspection of connectors and joints, CCR checks and record keeping. Condition trends in the records show deterioration before a failure occurs.

AGL series circuit troubleshooting

Troubleshooting a series circuit starts with the symptom: all lights out points to power, control or CCR, while one light out points to the lamp, transformer or secondary. Isolate, measure and locate the fault before repairing, then retest.

AGL series circuit testing procedure

A series circuit test sequence starts with isolating and making the circuit safe, then visual checks, insulation resistance and continuity or loop resistance tests, followed by energising and checking the current. Follow the approved test plan for methods and limits.

AGL series circuit selection guide

Selecting equipment for a series circuit means matching the CCR, cable, transformers and connectors to the circuit current, voltage, load and environment. Check that every part is compatible with the others.

AGL series circuit technical guide

This technical guide view of the series circuit links the working principle to design, installation, testing and fault finding. Learn the primary and secondary split first, because most fault logic follows from it.

AGL series circuit standards

Series circuit standards include the aerodrome lighting provisions of ICAO and national authorities, FAA equipment specifications, IEC and Indian standards for cables, connectors and equipment. The project specification names the ones that apply.

AGL series circuit preventive maintenance

Preventive maintenance of a series circuit follows a planned schedule: inspect and test insulation and loop resistance, check connectors, joints and the CCR, and record results. Planned work finds problems before they cause outages.

Exam & Interview

EXAM / INTERVIEW QUESTIONS

What is the AGL primary circuit?

The CCR-fed series circuit containing the primary cable and the primary windings of the isolation transformers.

What is the secondary circuit?

The individual circuit connecting an isolation transformer to its AGL fixture.

Why is the primary circuit a series circuit?

The primary windings of the isolation transformers are connected into a continuous series loop supplied by the CCR.

Why are isolation transformers used?

To provide electrical isolation and transfer power from the primary series circuit to individual fittings.

What controls primary current?

The CCR.

Is primary current always equal to secondary current?

No. It depends on the transformer configuration.

Can one secondary light fail while the primary circuit continues operating?

Yes. A secondary-side or fixture failure does not necessarily open the primary series loop.

What happens when the primary cable opens?

The series path is interrupted and current stops, so all the lights on that circuit go out and the CCR open-circuit protection normally operates.

What is the main difference between primary and secondary cable?

Primary cable forms the common series circuit; secondary cable connects an individual transformer to its fitting.

Why is cable resistance important?

It affects voltage drop, power loss and the total electrical requirement of the series circuit.

What is the basic primary chain?

CCR → Primary Cable → Transformer Primary → Primary Cable → Return.

What is the basic secondary chain?

Transformer Secondary → Secondary Cable → Connector → Fixture.

Why does the CCR output voltage change?

The CCR regulates current and develops the voltage the connected circuit impedance requires, within its design limits.

Why can a primary cable fault affect many lights?

The fixtures share one series loop. An open circuit darkens the whole circuit, and a short or double earth fault can bypass the lights in a section.

Why is a secondary fault usually localised?

Each transformer normally serves an individual fitting through its own secondary circuit.

What happens when secondary loads are disconnected?

The primary transformer remains in the series circuit, but enough disconnected loads can alter total circuit loading and electrical behaviour.

What matters more in primary-circuit design: voltage or current?

Both matter, but the CCR's controlled parameter is the series current; voltage capability follows the total circuit requirement.

Why must transformer primary current match the CCR circuit?

The primary winding is part of the series circuit and must be designed for the actual regulated current.

How to test an AGL series circuit?

Isolate the circuit and make it safe, then check it visually. Test insulation resistance and continuity or loop resistance of the primary cable and connectors, then energise and check the CCR output current at the brightness steps. Follow the approved test plan, standard and manufacturer data for methods and limits.

Final Study Takeaway

FINAL STUDY TAKEAWAY

The primary is the common CCR-controlled series circuit: CCR + primary cable + transformer primaries + connectors + return. The secondary is the individual fitting circuit: transformer secondary + secondary cable + connector + fixture. The primary controls and distributes the series current, the isolation transformer provides the interface and isolation, and the secondary supplies the individual fixture.

AGL circuit knowledge = CCR + Primary cable + Series circuit + Isolation transformer + Secondary cable + Connector + Fixture + Testing + Photometry.

Field Insight

ENGINEERING & EXPERT NOTES

By Rahul Sharma

Airfield Ground Lighting Specialist

Treat the Primary as Hazardous Until Proved Dead

Safety

A series circuit can hold dangerous voltage even when lights appear off. Follow isolation and test-for-dead procedures every time.

Section the Circuit to Find the Fault

Fault Location

Splitting the primary into parts and testing each narrows the search far faster than walking the whole route.

Read Current and Voltage Together

Diagnosis

A circuit holding current but needing more voltage than before is telling you resistance has grown. Log both at each step.

Most Secondary Trouble Is at the Connector or Lead

Secondary

Check terminations and secondary cable before replacing a transformer or a fixture.

References

REFERENCES & FURTHER READING

These notes are a study aid. Verify details against the primary sources below (FAA-based systems).

#	Source	Use it for
1	FAA AC 150/5345-10H – Constant Current Regulators and Regulator Monitors	CCR classes, regulated current, brightness steps.
2	FAA AC 150/5345-47C – Series to Series Isolation Transformers	L-830/L-831 types, ratings, construction, testing.
3	FAA AC 150/5345-7F – L-824 Underground Electrical Cable for Airport Lighting Circuits	Primary cable specification.
4	FAA AC 150/5345-26E – L-823 Plug and Receptacle, Cable Connectors	Connectors for cables, transformer leads and fixture leads.
5	FAA AC 150/5340-30J – Design and Installation Details for Airport Visual Aids	Installation guidance and recommendations.
6	FAA AC 150/5340-26C – Maintenance of Airport Visual Aid Facilities	Series-circuit safety, insulation-resistance testing and troubleshooting.
7	ICAO Annex 14, Volume I, Chapter 8 (Electrical Systems) and ICAO Doc 9157 Part 5	International practice for series circuits, secondary power and cabling; check the current edition.

Check the editions. For any airport, check the approved project drawings, airport technical specification, national authority requirements, equipment certification and manufacturer's instructions together with the applicable FAA/ICAO requirements.

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PRIMARY & SECONDARY CIRCUITS COMPLETE NOTES