| Aspect | Verdict | |--------|---------| | Maturity | Very stable, decades of field use | | Ease of integration | Moderate (requires current-loop hardware, not standard serial) | | Security | Poor – no authentication, no encryption | | Future-proof | Declining, but still supported by Gilbarco for legacy | | Best for | Retrofit, fleet sites, budget-limited third-party controllers | | Worst for | New high-volume retail, EMV compliance, remote diagnostics |
Documentation references (needed for development):
If you are planning to buy a third-party controller that claims two-wire support, ask the vendor: | Aspect | Verdict | |--------|---------| | Maturity
If you are developing your own controller, start with a known current-loop chip like LTC1487 or MAX491 configured for loop mode, and capture bus traffic with a logic analyzer first (e.g., Saleae) before writing any code.
The controller software must be programmed to interpret the specific timing and voltage levels associated with the Gilbarco Two-Wire standard. If you are planning to buy a third-party
| Parameter | Value | |-----------|-------| | Loop voltage open | 12–24V DC (dispenser provides) | | Loop current low | 0–4 mA (logic 0) | | Loop current high | 18–30 mA (logic 1) | | Baud rate | 1200 bps (typical), some older are 600 bps | | Data format | 1 start bit, 7 data bits, 1 parity (even), 1 stop bit | | Character framing | Asynchronous, half-duplex | | Max distance | 2000 ft (600 m) with shielded twisted pair |
⚠️ Common mistake: Using RS-232 or RS-485 transceivers directly – will damage the dispenser’s interface. You need a current-loop converter (e.g., B&B Electronics 232CL, or build with 4N35 optos). If you are developing your own controller, start
A third-party controller must implement the following command sets:
The Gilbarco TwoWire (also called Two‑Wire Multiplex or TW) protocol is a low‑level serial communication protocol used between a dispenser controller (pump head) and a point‑of‑sale / site controller or third‑party pump controller. It carries commands and status for fuel selection, nozzle status, dispenser electronics, price/volume totals, authorizations, and misc. device diagnostics over a two‑wire physical link.
The two-wire protocol returns pulses as a frequency. The new converters output these as standard quadrature encoder pulses or Modbus registers. Your third-party pump controller can now read real-time flow data with sub-penny accuracy.