EL14 Horizontal Audio Isolation Transformer, Through-Hole PCB Mount, 300 Hz - 3.4 kHz, 1:1 Turns Ratio, EI1401 / EI1402, 16 x 8.5 mm

1. Product Name

EL14 horizontal audio isolation transformer for voice and data coupling, available as EI1401 or EI1402. Precision ferrite core, primary winding on pins 1-2, secondary winding on pins 4-3, externally insulated with yellow tape, four through-hole pins, frequency range 300 Hz to 3.4 kHz, maximum body length 16 mm, height 8.5 mm.

Overview. The coil is wound on an insulated bobbin within the core window and encapsulated with yellow tape; four pins extend from the pin header at the bottom in two rows. Nothing protrudes above the top of the core, which is why the assembled height stays at 8.5 mm.

The horizontal package is chosen for height reasons rather than footprint: low-profile boards typically have limited vertical space above the surface, and a flat-mounted component uses existing space instead of adding height.

2. Features

Integrated isolation. The transformer protects the output stage of the front-end equipment from damage on the other side of the isolation barrier, which is what an isolation device does.

Voice and data coupling. The winding design is intended for interstage signal transfer rather than power transmission, so the audio band passes through completely while ground loops do not conduct.

300 Hz to 3.4 kHz band. Covers the telephony voice band, which is the rated operating band of this device; no performance claims are made beyond this range.

Eliminates ground loop hum. Breaks the AC hum ground loop caused by a system being grounded at two points.

Bidirectional interference suppression. Reduces external interference pickup in both balanced and unbalanced transmission; one device covers both wiring schemes.

This photo shows two critical faces of the assembly: the tape wrapping and outer core legs are visible from the top, while the pin header is visible from the bottom. The pins are spaced 6 mm within a row and 12 mm between rows, so the plated holes determine the mounting orientation of the device before any markings are read.

3. Advantages

Low-profile horizontal package. The body sits flat, 8.5 mm above the board, allowing installation under covers or between other components on dense PCBs.

Standard through-hole pin layout. Four pins in two rows with 6 mm within-row spacing and 12 mm between-row spacing, so the package size is fixed and board layout can be completed without mechanical redesign.

Two variants in the same footprint. EI1401 and EI1402 share the pin pitch, 1:1 turns ratio, and 1500 V dielectric rating; selecting the variant sets the grade without changing the circuit board.

Customizable design. When neither standard variant fits the application, the winding can be customized to customer specifications.

Factory-direct supply. Standard devices are in stock and ready to ship, preventing lead times from becoming a bottleneck on the critical path.

These two views can be read without labels: the core legs extend along the body length, the coil pads sit beneath the pin header, and the tape wrapping fully covers the winding. This is the complete structure of the device — core, coil, insulation, pins — with no need for a potted enclosure or bracket.

4. Applications

Communication equipment. Coupling between the line side and the equipment side, where both sides must remain electrically isolated.

Medical electronic equipment. Signal paths requiring isolation from the patient-contact side, suitable for the low-level applications for which this device is rated.

Telephone and fax equipment. The 300 Hz to 3.4 kHz band is exactly the voice band carried by these terminal devices, and the 1:1 turns ratio keeps levels unchanged across the isolation barrier.

Inductive loudspeakers. Coupling to loops or induction coils without direct connection forming a ground loop path.

Both views show PCB assemblies: in the first, the device is seated with all four pins passing through the board; in the second, the pins are being soldered. The 8.5 mm standoff is the point shared by both images — the body maintains clearance from adjacent components without requiring any parts to be moved.

5. Application Specifications

The following specifications are the declared data for this model: product data, electrical parameter tables for each variant at 25 °C, outline and pin dimensions, and pin assignments.

5.1 Product Specifications

Item	Value
Product Name	EL14 horizontal audio transformer
Model	EL14, horizontal package
Variant Model	EI1401 and EI1402, see electrical specifications
Product Category	Audio isolation / voice and data coupling transformer
Mounting Type	Horizontal through-hole, PCB mount
Winding	Primary pins 1-2, secondary pins 4-3
Turns Ratio	1:1
Frequency Range	300 Hz - 3.4 kHz
Core	Precision ferrite core
Coil	Precision wound, primary 1-2, secondary 4-3
Insulation	Yellow tape insulation
Terminals	4 through-hole pins, 2 primary and 2 secondary
Reference Temperature	25 °C
Design Service	Custom design available

5.2 Electrical Specifications, Both Variants, 25 °C

Inductance is measured at 1 kHz with a 0.3 V test signal and is a minimum value; DC resistance tolerance is ±15%; dielectric withstand is 1500 V with 1 mA leakage limit for 60 seconds. The column headers DCR(1-3) and DCR(4-5) are as printed on the original data sheet; see the note below.

Variant	Turns Ratio	L(1-2)	L(3-4)	DCR(1-3)	DCR(4-5)	Dielectric Withstand
EI1401	1:1	780 mH	780 mH	260 Ω	260 Ω	1500 V
EI1402	1:1	1.0 H	1.0 H	290 Ω	290 Ω	1500 V

EL14 is the model, and the electrical parameter table below it lists two variants: EI1401 and EI1402. Both have a 1:1 turns ratio and a 1500 V rating; they differ in inductance and DC resistance, with EI1401 at 780 mH and 260 Ω and EI1402 at 1.0 H and 290 Ω. The variant code is prefixed with EI14 while the model is written as EL14, which is how the source data sheet is structured.

Two body dimensions are specified: a maximum length of 16 mm and a height of 8.5 ± 0.3 mm, both marked on the dimension view. A third body dimension is not given in the source data; instead, the pin layout is referenced: 6 ± 0.3 mm within-row spacing and 12 ± 0.3 mm between rows. Do not derive the body depth from the between-row pin spacing — these are not the same measurement.

This page references the structural, dimensional, electrical, and test data declared for the EL14 in the specification sheet at 25 °C. The specification sheet does not specify weight, minimum order quantity, or pricing, and none are given here. Additionally, the specification sheet does not include certificate numbers, so the CCC, CE, RoHS, and UL marks appearing in the provided renderings are outside the scope of this page's claims, and that image is not used. The core is described as a precision ferrite core; if your design assumes a laminated core based on the EL14 designation, please confirm the construction with the factory before committing to the design.