A Handy Guide to "Amphenol" Connectors

The 'Amphenol' connector is ubiquitous in the telephone world. This 50 position connector is the backbone of key system and PBX installations, yet nobody seems to really agree on what to call it.

This connector is popular in a number of other applications too; the 50 position version was also the standard connector for SCSI-1 equipment. The 36 position version was made popular by Centronics when they chose to use it as the connector for the interface to their Centronics 101 printer, a connector that would later go on to be a de-facto standard for low cost printers. The 24 position version was made popular by HP with their use of it for their HP-IB bus (later known as IEEE-488). For the purpose of this page, I'll be focusing on the 50 position connector, and its application to the field of telephony.


The Micro Ribbon connector, as Amphenol calls it, was invented by Robert S. Yopp. He filed for a patent for his invention in 1956, and US Patent 3,002,176 was granted to him in 19613. The Micro-Pierce connector was invented by Paul Peter Hoppe, Jr.; He filed his patent in 1972, an in 1975 was granted US Patent 3,926,4984.

Amphenol originally called it the "Micro Ribbon" connector1, and first used it to market their product in 1956. This is the 57 series of the connector, which was the soldered version of the connector. The insulation displacement 157 series was released in 1974, and was marketed as the "Micro-Pierce" connector2. I don't think I've ever heard a telephone installer use either of those names to describe the connector.

So What Do We Call Them?

What these are called typically depends on the application. For the purposes of this document, I'll refer to them as the most technically accurate term: Micro Ribbon connectors.

Gender Nomenclature


This connector is most often referred to as a "plug". Some manufacturers and distributors might refer to it as a "male" connector. It is most often found on cable ends. Most cables with connectors on both ends will have this connector on each end.

The plug is usually equipped with a BLUE dust cover.


This connector is most often referred to as a "receptacle". Some manufacturers and distributors might refer to it as a "female" connector. It is most often found on equipment in its panel mounted form. It is typically only used on a cable when it is a cable that is terminated on a piece of equipment, or as part of an "extension" cable designed to add length to an existing cable.

The receptacle is usually equipped with a RED dust cover.

Manufacturers & Tooling

Quick Jump



Amphenol was of course the first manufacturer of the Micro Ribbon connectors. Amphenol continues to manufacture the Micro-Ribbon/57 series and Micro-Pierce/157 series connectors to this day.


For the Micro-Pierce/157 series of connectors, Amphenol provided a number of tools to facilitate wire insertion:


P/N 356-236 Mass Termination Tool (157 Series)

This tool trims and punches down all 50 wires simultaneously.

P/N 356-246 Tele-Pierce Tool (157 Series)

Similar in design and operation to the 356-236.

P/N 356-265 Deca-Pierce Field Terminator Tool (157 Series)

Trims and punches down only 10 wires at a time.

P/N 494-57 Fast 57 Field Tool

An earlier version of the design? Not sure.


TRW/Cinch produced what is essentially a direct copy of the Amphenol design. Tooling designed for Amphenol brand connectors is compatible with TRW/Cinch connectors and vice-versa. In later years, it appears TRW/Cinch produced a plastic version of the Micro Ribbon connector, but one that was compatible with existing tooling.



Certi-Clinch Portable Termination Tool

Known to the Bell System as KS-21749.

Uni-Clinch Portable Termination Tool


AMP, originally Aircraft and Marine Products, is not to be confused with, and entirely unrelated to Amphenol. AMP offered their own line of IDC terminated Micro Ribbon connectors. The AMP connector has a single piece all plastic body, with a slide-on plastic shell. It became most popular version of the Micro Ribbon connector among PBX installers.


There are two basic part numbers for the connectors used for telecom purposes:

AMP has a rather confusing and non-orthogonal system of part numbers for these connectors. The prefix and suffix numbers indicate the cable size the hood is designed for, the colour of the connector and hood, whether a dust cover is included, and how the connector is packaged. There's no rhyme or reason for how the prefix or suffix numbers are applied. The part numbers in bold are usually the cheapest and most appropriate-for-telephone versions that can be ordered on DigiKey.

PackagingTypeCable RangeDust CoverColorPart Number
BaggedReceptacle0.350" - 0.425"NoBlack5229913-1
BaggedReceptacle0.350" - 0.425"NoGray5229913-4
BaggedReceptacle0.350" - 0.425"YesBlack1-5229913-1
BaggedReceptacle0.350" - 0.425"YesGray1-5229913-4 (discontinued)
BaggedReceptacle0.425" - 0.500"NoBlack2-5229913-1
BaggedReceptacle0.425" - 0.500"YesBlack3-5229913-1
BulkReceptacle0.350" - 0.425"NoBlack6-5229913-1
BulkReceptacle0.350" - 0.425"YesBlack6-5229913-3
BulkReceptacle0.350" - 0.425"YesGray6-5229913-4 (discontinued)
BulkReceptacle0.300" - 0.325"YesBlack6-5229913-7 (discontinued)
BaggedPlug0.350" - 0.425"NoBlack5229912-1
BaggedPlug0.350" - 0.425"NoGray5229912-4
BaggedPlug0.350" - 0.425"YesBlack1-5229912-1
BaggedPlug0.425" - 0.500"NoBlack2-5229912-1
BaggedPlug0.425" - 0.500"YesBlack3-5229912-1
BulkPlug0.350" - 0.425"NoBlack6-5229912-1
BulkPlug0.350" - 0.425"YesBlack6-5229912-3
BulkPlug0.350" - 0.425"YesGray6-5229912-4
BulkPlug0.300" - 0.325"YesBlack6-5229912-7 (discontinued)

NOTE: AMP's older part numbers are one digit shorter, so if you want to search for these connectors on ebay, try searching for "229912" or "229913".


P/N 229384-1 T-Grip Hand Insertion Tool
P/N 229378-1 CHAMP MI-1 "Butterfly Tool"

The infamous butterfly tool.

P/N 229451-1 CHAMP Palm Inserter

Facilitates terminating one wire at a time on the connector, in a manner slightly less fiddly than using the 229384-1 T-Grip Hand Insertion Tool. For some reason this tool is painfully expensive.

Viking Industries

I don't know much about this one. The tool shown below appears from time to time on eBay. From their patent, this system appears to be very similar to the AMP CHAMP design6.


I currently have no information on Viking's connectors.


P/N 000407-0100 Vitel-F Pushover Tool


Research in progress.



4162 MS2 Universal Hand Terminator Tool

Bell System KS Numbers

The Bell system KS numbers refer to the Amphenol/Cinch style of connector.




  1. USPTO Registration No. 1,225,773
  2. USPTO Registration No. 1,026,629
  3. US Patent 3,002,176 - Multiple Contact Electrical Connector
  4. US Patent 3,926,498 - Electrical Connector and Insulation-Piercing Contact Member, re-issued as Re. 31,132, as it would appear the original patent as granted was missing a page. Oops.
  5. US Patent 3,953,925 - Installation Tool and Method for Installing a Plurality of Wires on an Electrical Connector Frame