Choose by the machine's controller, not by preference. Machines built around MDB talk to a payment device over a two-way serial bus. Machines that only accept a credit signal use pulses or a contact closure. Some machines support neither cleanly, so identify the interface before you buy hardware.
This guide explains the practical differences and how to find out which interface a machine has.
The protocol difference in plain language
MDB (Multi-Drop Bus) is a serial protocol between the machine's controller and peripherals such as cashless readers. The two sides exchange structured messages, for example a vend request, an approval, and a vend success or failure report. That lets the machine and reader agree on what happened. For how MDB levels differ, see Understanding MDB Levels.
Pulse is a simpler signal. The reader sends a number of pulses, or closes a contact, and the machine treats that as credit. The pulse count and timing are configured per machine. Pulse normally flows one way, so the reader does not automatically learn whether the machine started or delivered. For the modernization angle, see Modernize Your Pulse-Based Systems.
| Attribute | MDB | Pulse |
|---|---|---|
| Signal | Two-way serial bus | Pulse train or contact closure, usually one way |
| Machine feedback | Structured vend status messages, depending on protocol level | Usually none, may need a separate sensing input |
| Typical equipment | Vending machines and similar unattended equipment | Laundry, car wash, amusement, and some older machines (varies by model) |
| Pricing | Price handled through controller messages | Price tied to pulse count, changed by configuration |
| Power | Supplied through the machine's MDB connection, confirm limits in the spec and manual | Often needs a separate power source or a tap from the machine, verify per model |
| Interface hardware | MDB cable and a reader with MDB support | Pulse interface or relay wired to the credit input |
| Installation dependencies | Controller firmware level and settings | Wiring access, coin input handling, pulse settings |
A pulse alone does not confirm that a cycle started or a product was delivered. Plan how the system will detect that separately.
How to identify the interface
- Record the machine make, model, and serial number, plus any label on the controller board.
- Search the manual or service guide for MDB, cashless, pulse, coin mechanism, or card reader port.
- Inspect the controller for a labeled MDB or cashless connector, and note how the coin or credit input is wired.
- Ask the manufacturer or distributor which interface the model supports, and keep the answer in writing.
- Photograph the board, connectors, and wiring before ordering hardware.
Do not assume. Two machines from the same family can differ by firmware or option kit.
Compatibility checklist
| Check | Question to answer | Done |
|---|---|---|
| Interface | MDB, pulse, or something else, confirmed in writing? | ☐ |
| Protocol level | If MDB, which level does the controller support? | ☐ |
| Power | How is the reader powered and what current is available? | ☐ |
| Interface hardware | Which cable, adapter, or pulse board is required? | ☐ |
| Machine feedback | How will the system know the vend or cycle started? | ☐ |
| Pricing | How are prices set, and who changes them later? | ☐ |
| Installation | Is there physical access, and does the install affect warranty? | ☐ |
| Connectivity | How does the reader get online at the site? | ☐ |
| Pilot | Can one machine be tested before a wider rollout? | ☐ |
Hardware and installation pricing varies by model and site, so scope it after the interface is confirmed.
FAQs
Is MDB always better than pulse?
Not as a rule. MDB gives richer two-way messaging, but you use the interface the machine provides. The right choice is the one the controller supports.
Can a pulse machine confirm that a cycle started?
Not from the pulse itself. You may need a separate input or sensing method, and the design should handle the ambiguous cases.
Do all laundry machines use pulse?
No. Interfaces vary by manufacturer and model, so check each machine.
Can I switch an MDB machine to pulse?
Only if the machine supports it. Ask the manufacturer rather than modifying the controller.
Next step
If you can share your machine models, controller details, processor, and project requirements, we can help identify the right interface. See the MDB integration page and the Pulse overview.
Sources
▸ Understanding MDB Levels and How They Shape Vending Payments
Software executive with over three decades of experience. Focus primarily on the payment industry and FinTech technologies