Est. 1985
Current Version ISO 7638-1/-2:2018
Scope 7-pin 24V/12V ABS/EBS trailer connectors
Regionality Worldwide

The first edition of the standard ISO 7638 was issued in 1985. Its purpose was to create a standardized system for the transfer of signals regarding the anti-lock braking system (ABS) from towing vehicles to heavy trailers. In 1997, the standard was split into two parts with ISO 7638-1 covering 24V systems and ISO 7638-2 covering 12V systems. The next review was issued in 2003. It updated the previous edition concenring requirements for the connection of running gear. The latest version of the two-part standard is from 2018.

Application and features of ISO 7638-1 and -2

The ABS/EBS (Electronic Braking System) connectors for truck and trailer are used on nearly every commercial vehicle type with ABS/EBS System. They include various safety features: If a plug is incorrectly plugged in, it is automatically ejected by an ejector pin. Furthermore, the socket and plug housing of the 12V and the 24V system show different codings. This feature effectively avoids an accidental connection between components of the standard ISO 7638-1 and ISO 7638-2 thus protecting the electrical system from possible damage.

Pins 6 and 7 of the 7-pin standard are used for CAN-Bus data lines according to ISO 11992. As a CAN-Bus connection is not necessary for the functionality of the ABS system, there is also a 5-pin variant of this connector without pins 6 and 7.

Scope of ISO 7638-1 and -2

The standards ISO 7638-1 and 7638-2 specify

  • the dimensional characteristics of 7-pin connectors for the electrical connection of braking systems and running gear used in towing and towed vehicles with 24 V (ISO 7638-1) or 12 V (ISO 7638-2) nominal supply voltage
  • the contact allocation as well as tests and requirements for the trailer connector system
  • a park socket for receiving and storing the plug when it is disconnected

Contact Allocation for Connectors According to ISO 7638-1 (24V) and 7638-2 (12V)

 Contact no.FunctionCross-sectional areaCore insulation colorDesignation according to DIN 72552
1Plus electrovalve4 mm²red30
2Plus electronics1,5 mm²black15
3Minus electronics1,5 mm²yellow31
4Minus electrovalve4 mm²brown31
5Warning devicea1,5 mm²white--
6CAN_Hb1,5 mm²white/green--
7CAN_Lb1,5 mm²white/brown


a The warning device is controlled through Contact 5. This contact has an open circuit during normal operation.
b In accordance with ISO 11992-1 and ISO 11992-2