Transaction Flow Options using EHI

The External Host Interface (EHI) is a Thredd system which sends real-time payment authorisation requests and other types of financial messages to your systems.

Your systems must be able to receive and process messages sent from EHI to your external host endpoint. You can specify your EHI endpoints and other EHI configuration options using the Thredd Product Setup Form (PSF). Your Implementation Manager will then set this up on the Thredd system.

Depending on your EHI Mode, you may need to authorise (approve or decline) payment requests on a card and adjust the card balance held in your systems to reflect any authorisation or financial messages received. Detailed information on how to do this is provided in the External Host Interface (EHI) Guide.

EHI Modes

Not sure which mode you need? To find the right mode for your business, try our EHI Transaction Option Selector Wizard.

EHI supports the following options:

Modes	Type of Processing	Description
1	Gateway Processing	Your systems maintain the balance and perform authorisation.
2	Cooperative Processing	Thredd maintains the balance and performs authorisation. You can override an approval decision. In Approval with Load your systems maintain the balance and can update the Thredd-maintained balance.
3	Full-Service Processing	Thredd maintains the balance and performs authorisation. You receive a read-only response.
4	Gateway Processing with Stand-In	Your systems maintain the balance and perform authorisation. Thredd provides Stand-In authorisation if your systems are unavailable.

For more information, see the External Host Interface (EHI) Guide.