| Optical |  |  | ZVEI interface, for communication and testing, M-Bus protocol, 2400 baud | 
| M-Bus |  |  | Configurable telegram, according to EN1434-3, data reading and parametrization are via two wires with polarity reversal protection, auto baud detect (300 and 2400 baud), 2 M-Bus with 2 primary adresses | 
| L-Bus |  |  | Adapter for external radio module, configurable telegram, according to EN13757-3, data reading and parametrization are via two wires with polarity reversal protection. | 
| NB-IoT* |  |  | Compatible in Slot 1 with internal antenna, with external D-Cell battery, 13+1 years battery lifetime with daily upload of 24 hourly values. Configurable with NFC connection via OTC App (AppStore Android). | 
| RS232 |  |  | Serial interface for communication with external devices, a special data cable is required, M-Bus protocol, 300 and 2400 baud | 
| RS485 |  |  | Serial interface for communication with external devices, power supply with 12 V ± 5 V, M-Bus protocol, 2400 baud | 
| Pulse output |  |  | Module with 2 Open Collector pulse outputs (potential-free), output 1:  4 Hz (pulse width 125 ms), pulse or static conditions (e.g. errors), output 2: 200 Hz (pulse width ≥ 5 ms), ratio: pulse duration / pulse break ~ 1:1, configurable via IZAR@MOBILE 2 software. | 
| Pulse input |  |  | Module with 2 pulse inputs, max. 20 Hz, configurable via IZAR@MOBILE 2 software, data can be transferred remotely. | 
| Combined pulse in-/output |  |  | Module with 2 pulse inputs and 1 pulse output, configurable via IZAR@MOBILE 2 software, needed for leak detection. | 
| Analogue output |  |  | Module for 4 ... 20 mA with 2 programmable passive outputs, programmable value in case of error. | 
* Starting with August 1, 2025, only devices with firmware F04.006 or newer may be combined with NB-IoT modules with firmware 1.4.0 or
newer, in order to ensure compliance with the essential requirements according to art. 3(3) d and art. 3(3) e of Directive 2014/53/EU (‘RED
Cybersecurity’). The firmware version can be read out with the OTC app.