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newSchoolWorks.com › VoTechWorks › Business & Cross-Cutting › Locksmith & Security Systems › Electronic Locks: Installation, Programming, and Servicing › Lesson 1
BUS-LOCK72-07 · Lesson 1 · 12 clock hours · theory

Electronic Lock Technology: Types, Principles, and Power

Objective. Students will correctly classify at least eight electronic lock types by operating principle and specify the appropriate power supply configuration for each, scoring 80% or above on a written identification quiz.

⚠ Pending professional review

This lesson, its worked examples and its practice questions has not yet been verified by a credentialed professional in the field or by a certification or approval body. It is a study draft and may contain errors. Do not use it as instructions for work on a job site or on live equipment. Always follow your instructor, your supervising professional, and current official references and regulations.

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What Is an Electronic Lock?

An electronic lock uses an electrical signal — rather than purely mechanical means — to control whether a door can be opened. A credential (PIN, card, fingerprint, or wireless signal) is presented to a reader or sensor; the control circuit evaluates it and either releases or holds a locking mechanism. Every electronic lock therefore has three parts: a credential interface, a control circuit, and an electromechanical actuator.

Eight Major Electronic Lock Types

1. Keypad Locks

A keypad lock uses a numeric or alphanumeric PIN entered by the user. The onboard microprocessor compares the input against stored codes. Keypad locks are stand-alone or network-capable and are common on residential and light-commercial doors. They can be battery-powered (typically 9 V or four AA cells) or hardwired at 12 V DC.

2. Proximity Readers — 125 kHz (Low-Frequency)

Low-frequency proximity cards and fobs use passive RFID at 125 kHz (common formats include HID Prox and EM4100). The reader energizes the card's coil; the card broadcasts a fixed facility code and card number. Because the credential data is static, 125 kHz systems offer lower security than newer formats. Readers typically require 12 V DC at low current and connect to an access control panel that drives a separate door-side actuator.

3. Proximity Readers — 13.56 MHz (High-Frequency / Smart Card)

High-frequency smart cards (MIFARE, DESFire, iCLASS) operate at 13.56 MHz and support encrypted, mutual-authentication protocols. Data can be rewritten or updated. These systems are preferred for higher-security applications. Power requirements are similar to 125 kHz readers (12–24 V DC) but confirm with the specific manufacturer's spec sheet.

4. Biometric Units — Fingerprint and Retinal

Biometric locks capture a physiological trait and compare it to an enrolled template. Fingerprint readers scan ridge patterns using optical or capacitive sensors. Retinal/iris readers map vascular patterns using near-infrared imaging. Biometric units have higher current demands because of onboard processors and sensors; many require 12 V DC at 500 mA or more and a dedicated lock power supply when they control an electrified actuator.

5. Bluetooth Low Energy (BLE) Locks

BLE locks communicate with a smartphone or BLE credential at 2.4 GHz using very short data bursts to conserve power. They are commonly battery-operated (4 AA or a lithium pack) and managed through a mobile app or cloud platform. Read range is typically a few feet to about 30 feet depending on device and environment. BLE is classified as a short-range wireless access technology.

6. Wi-Fi–Enabled Locks

Wi-Fi locks connect directly to an 802.11 network, enabling real-time remote management, audit logs, and over-the-air firmware updates without a separate gateway. The continuous Wi-Fi radio draws significantly more current than BLE; battery life is shorter, making hardwired or frequent battery-change schedules necessary for busy openings.

7. Electrified Strikes

An electric strike replaces a conventional strike plate. Its pivoting keeper releases when energized (or de-energized, depending on the model), allowing the latch to pass. Two safety modes exist:

Always verify local fire and building codes before specifying fail-safe vs. fail-secure. Electric strikes operate at 12 V DC or 24 V DC (some accept both); inrush current at engagement can be two to three times the holding current.

8. Magnetic Locks (Maglocks)

A maglock uses an electromagnet mounted on the door frame and a steel armature plate on the door. When energized the magnet holds the door closed. Maglocks are inherently fail-safe — power loss releases the door — which is why life-safety codes require them to integrate with fire alarm systems and request-to-exit (REX) devices. Holding force ratings range widely; always match the rated force to the door and traffic level. Maglocks typically run on 12 V DC or 24 V DC and draw continuous current while locked.

Electric Latch Retraction (ELR) Devices

An ELR device is motorized hardware (mortise lock or exit device) that retracts the latch bolt electrically for remote or access-controlled release while the door remains mechanically secure otherwise. These units often require 24 V DC and higher current than a simple strike because of the motor load.

Power Supply Fundamentals

Most electronic locks and readers run on 12 V DC or 24 V DC. Key concepts:

Safety Points

Key terms9

Fail-safeA lock mode in which the device unlocks (releases) when electrical power is lost, ensuring free egress during a power failure or fire-alarm event.
Fail-secureA lock mode in which the device remains locked when electrical power is lost, preventing unauthorized entry during a power outage.
Electrified strikeAn electrically controlled strike plate whose pivoting keeper is released by an electrical signal, allowing the door latch to retract without turning a knob or lever.
Magnetic lock (maglock)A locking device that uses an electromagnet and a steel armature plate to hold a door closed; inherently fail-safe because power loss releases the door.
Proximity readerA credential reader that uses radio-frequency induction to communicate with a passive card or fob without physical contact; common frequencies are 125 kHz and 13.56 MHz.
Biometric lockAn access-control device that identifies users by a measurable physiological characteristic such as a fingerprint ridge pattern or iris map.
Inrush currentThe brief, elevated current demand a solenoid or motor draws at the instant of activation, which can be several times higher than the steady-state holding current.
Electric latch retraction (ELR)Motorized hardware that electrically retracts a door latch bolt for remote or access-controlled entry while otherwise functioning as conventional mechanical hardware.
Dedicated lock power supplyA separate, code-compliant power supply unit with battery backup used to power electrified door hardware independently from the access control panel's output.

Worked examples4

1. A maglock is rated 12 V DC at 500 mA continuous. A proximity reader on the same door is rated 12 V DC at 150 mA. What is the minimum current the power supply must deliver for these two devices, and what is the recommended supply capacity including 25% headroom?
  1. Step 1 — Add all load currents: 500 mA (maglock) + 150 mA (reader) = 650 mA total load.
  2. Step 2 — Calculate 25% headroom: 650 mA × 1.25 = 812.5 mA.
  3. Step 3 — Round up to the next standard supply rating: choose a power supply rated at least 1 A (1000 mA) at 12 V DC.
Answer: Minimum load is 650 mA; with 25% headroom the calculation yields 812.5 mA, so select a power supply rated at least 1 A at 12 V DC.
2. You measure the voltage across a keypad lock's power terminals with a digital multimeter and read 10.8 V DC. The manufacturer's spec sheet states the lock requires 12 V DC ± 10%. Is the supply voltage within acceptable range?
  1. Step 1 — Calculate the lower tolerance limit: 12 V × (1 − 0.10) = 12 V × 0.90 = 10.8 V DC.
  2. Step 2 — Compare measured value to the limit: 10.8 V measured equals exactly 10.8 V, the lowest acceptable voltage.
  3. Step 3 — Conclusion: the reading is at the edge of the tolerance band. While technically within spec, any further voltage drop (due to wire resistance under load) could push the lock below its operating range, so the supply or wiring should be inspected.
Answer: 10.8 V DC is exactly at the lower limit of the ±10% tolerance band. The voltage is marginally acceptable but warrants checking the supply output and wire run for additional voltage drop under full load.
3. An electric strike is rated 24 V DC at 300 mA holding current and has a manufacturer-stated inrush current of three times the holding current. What is the peak inrush current the power supply and fuse must tolerate at the moment the strike activates?
  1. Step 1 — Identify holding current: 300 mA.
  2. Step 2 — Multiply by the inrush factor: 300 mA × 3 = 900 mA peak inrush.
  3. Step 3 — Ensure the power supply is rated above 900 mA at 24 V, and select a slow-blow fuse rated at or above 900 mA to avoid nuisance tripping during activation.
Answer: Peak inrush current is 900 mA. The power supply and fuse must be sized to handle at least 900 mA momentarily at 24 V DC.
4. A security director wants to install a maglock on a stairwell exit door that is a required means of egress. A vendor proposes a fail-secure maglock to prevent tailgating. Is this configuration correct? Why or why not?
  1. Step 1 — Identify the lock's power-loss behavior: fail-secure means the door stays locked when power is lost.
  2. Step 2 — Apply the egress rule: a required means-of-egress door must allow free passage during a fire alarm or power failure.
  3. Step 3 — Conclusion: a fail-secure maglock is not appropriate on a required egress door. A fail-safe maglock (which releases on power loss and on fire-alarm activation) is the correct specification.
Answer: The fail-secure proposal is incorrect. A required egress door must use a fail-safe maglock that releases automatically on power loss and integrates with the fire alarm system so occupants can exit freely in an emergency.
In class: Instructor-led lecture and slide presentation covering keypad locks, proximity (125 kHz and 13.56 MHz) readers, biometric fingerprint/retinal units, Bluetooth Low Energy locks, Wi-Fi-enabled locks, electrified strikes (fail-safe vs. fail-secure), magnetic locks (maglocks), and electric latch retraction devices; students annotate a provided reference sheet with key parameters for each type. · Power supply lab exercise: students measure DC voltage and current draw of five different electronic lock samples using a digital multimeter, complete a table comparing rated vs. measured values, and identify which units require a dedicated lock power supply versus drawing from an access control panel. · Small-group sorting activity where students receive a set of 20 scenario cards describing installation sites and security requirements and must select the correct lock type for each, then present and justify two choices to the class; instructor provides corrective feedback.
Materials: Assorted electronic lock samples (keypad deadbolt, proximity reader/electric strike pair, maglock, biometric stand-alone unit, BLE-enabled knob), digital multimeters, manufacturer specification sheets, DC bench power supplies set to 12 V and 24 V, instructor slide deck, student reference sheets, ALOA study guide chapters on electromechanical hardware
Check: Written 25-question identification and classification quiz; students must score 20/25 (80%) to pass. Items include selecting fail-safe vs. fail-secure for a given egress scenario and matching power supply requirements to lock types.

Practice check8

Answer each question, then check it. Nothing is recorded; this is your own practice.

Electrified hardware and access control
1. A hospital exit stairwell door requires an electrified strike. Life-safety codes mandate free egress if the fire alarm activates. Which mode must the strike operate in?
Electronic security technology
2. Which of the following RFID frequencies is associated with smart cards that support encrypted, mutual-authentication protocols such as MIFARE and DESFire?
Power supply and electrical measurement
3. A technician measures 10.2 V DC at the power terminals of a 12 V DC magnetic lock under full load. The manufacturer specifies 12 V DC ± 10%. What is the most accurate conclusion?
Electrified hardware and access control
4. What is the primary reason a magnetic lock is described as inherently fail-safe?
Power supply and electrical measurement
5. A proximity reader rated at 12 V DC / 100 mA and an electric strike rated at 12 V DC / 400 mA are connected to the same power supply. Applying a 25% headroom margin, what is the minimum power supply capacity required?
Electrified hardware and access control
6. Which electronic lock type uses a continuous electrical current to maintain its locked state, and therefore must integrate with a fire alarm system to release during an emergency?
Electronic security technology
7. A Bluetooth Low Energy (BLE) lock is best described as communicating via which technology?
Power supply and electrical measurement
8. During a power supply sizing exercise, a technician learns that an electric strike has a holding current of 250 mA and an inrush current of three times the holding current. What peak current must the fuse and power supply tolerate at the moment the strike activates?
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