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1/4" LONG FRAME TELEPHONE TWIN JACKS

1. MT389
2. MT388
3. WMT389

click here to download a schematic drawing
(you will need to have Adobe Acrobat installed on your system to do this)

High quality telephone jacks are essentially doubled versions of MT-Jax®. Twin-Jax® are used in Switchcraft Series 2400, 2600 and JP® Jack Panels and other standard jack panels. Twin-Jax® have direct WEco equivalents.
MT388 AND WMT388
Frame mounting ears are on 1.375 inch centers, and bushings are on .625 inch centers. Jacks are double, 2-conductor type with a crossover wiring feature. If a mating plug is inserted in either bushing, crossover contacts are opened (see schematic). MT388 (solder lugs) is equivalent to WEco jack 410A, 410C and 410D. WMT388 (wire-wrapping) is equivalent to WEco 410AM.
MT389 AND WMT389
Double, 3-conductor jacks with both the tip and ring circuits interconnected (crossover wired) so if a plug is inserted in either jack, common circuits are opened (see schematic). MT-389 (solder lugs) is equivalent to WEco 482A. WMT389 (wire-wrapping) is equivalent to WEco 482AM and 482BM.
SPECIFICATIONS
Frame and Stack Screws: Steel, plated with iridescent
iridite finish.
Springs: Copper alloy, spring tempered. Solder lugs are
solder coated.
Bushings: Nickel-plated copper alloy.
Contacts: Welded crossbar palladium in shunt circuits. Insulation: Rigid plastic (MIL-type PBE-P, per MIL
Specification LP-513C). Extruded plastic insulating
tubing through stack.
ORDERING
Order by part number from table.

Part Number¹

Adjusted for Plug Dim. "X" max. Inch (mm)

MT388 WEco types 298B and 347B MIL types M642/9-1 and M642/1-1
.562 (14.3)

ı WMT388 Switchcraft types 411, 412, 413, 420 .562 (14.3)

MT389 WEco type 310 MIL types M642/2-1 and M642/2-2 .594 (15.1)

WMT389 Switchcraft types 414 and 482 .562 (14.3)

ı Special Order only; contact Switchcraft.
1 Number MT388 is equivalent to MIL-type M641/11-1
2 Complete data for telephone and MIL-type plugs are contained in this section.
Mounting Screws: #6-32, Part Number P10725, can be ordered separately.
Contact Switchcraft. (Screws not supplied with jacks).

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Part Number¹	Adjusted for Plug	Dim. "X" max. Inch (mm)
MT388	WEco types 298B and 347B MIL types M642/9-1 and M642/1-1	.562 (14.3)
ı WMT388	Switchcraft types 411, 412, 413, 420	.562 (14.3)
MT389	WEco type 310 MIL types M642/2-1 and M642/2-2	.594 (15.1)
WMT389	Switchcraft types 414 and 482	.562 (14.3)
ı Special Order only; contact Switchcraft. 1 Number MT388 is equivalent to MIL-type M641/11-1 2 Complete data for telephone and MIL-type plugs are contained in this section. Mounting Screws: #6-32, Part Number P10725, can be ordered separately. Contact Switchcraft. (Screws not supplied with jacks).