The two-channel AD-KEB 20 GX is used to read in digital signals that are present as a contact or active 24V signal. The respective signal state is indicated on the device by means of a red LED. Device communication takes place via the RS485 bus interface and is implemented using the MODBUS RTU protocol.
The power supply and the RS485 bus connection are possible via the rear DIN rail connector. The device is equipped with two rotary coding switches with which the bus address can be set on the device.
An optical search function allows the localization of a single device in a network. For this purpose, the green LED is set in a time-limited flashing mode, between 1 and 255 seconds.
Interface settings as well as the device address can be modified during operation by means of Modbus commands.
All Modbus register addresses and associated commands are listed in the document attachment. The presettable absolute counters continuously add incoming pulses and are saved in a non-volatile memory every hour. The current counters are reset during readout to detect subsets.



Reading in digital signals in general electrical engineering, automation technology and in the water / wastewater sector.
For example: pulse counting with presettable counters or frequency measurement.

Specific characteristics

  • RS485 bus / Modbus RTU protocol
  • Rotary coding switch for bus address setting
  • Counter function
  • Frequency measurement
  • Switching Power Supply
  • Optical search function

Business data

Order number
Rail connector
Artnr: AD-GX-Connector
Zur Durchschleifung von Versorgungsspannung und RS485-Bus
Aufrastbar auf Tragschiene
(DIN EN 50022).
Customs tariff number / country of origin 8543 70 90 / Deutschland


Data sheet pdf en-keb20gx.pdf (211 kB)
Tender text zip (10 kB)
STEP file step gx.step (3 MB)
Safety instructions pdf ad-safety-instructions.pdf (43 kB)

Technical specifications

Input voltage 24 V DC / 3,5 mA (max. 30V)
Switching threshold ~ 17 V
Contact load 5 V / 1,5 mA
Frequency < 2200 Hz
Gate time 1 s
Accuracy +/- 0,3%
Counter 0...4294967295
Pulse width (counter) > 25 ms
Counting frequency < 20 Hz
Contact debouncing 20 ms
Counter storage Stündlich
Transmission behaviour
Response time Max. 15 ms
Software protocol Modbus-RTU
Data format 19200, e, 8, 1
Max. bus users 99
Bus termination 120 ohms both sides at the end
Max. length of bus 500 m (no spur lines)
Cable Twisted and shielded
Supply voltage 18 ... 30 V DC
Max. power consumption 800 mW (24V DC)
Dimensions (WxHxD) 6,2 x 92 x 101 mm³
Manner of fastening DIN rail mounting 35mm, EN 50022
Type of protection IP 20
Connection method Screw clamp
Bolting torque terminals 0,5 Nm
Wire cross section Max. 2,5 mm2
Weight ~ 70 g
Environmental conditions
Permissible ambient temperature -10 ... +50 °C
Storage and transport -10 ... +70 °C (no condensation)
Product family standard 1) EN 61326-1
Emission 2) EN 55011, CISPR11 Cl. A, Gr. 1
1) During checking, slight signal deviations are possible.
2) Warning:
This device is not intended to be used in residential areas and can not ensure adequate protection of radio reception in such environments.
Electrical safety requirements
Product family standard EN 61010-1
Galvanic isolation, test voltages
RS485 bus / power supply 1,5 kV, 50 Hz (1 min)
Digital input / Power supply 1.5 kV, 50 Hz (1 min)
Digital input / RS485 bus 1,5 kV, 50 Hz (1 min)
Digital input between themselves 0 kV
Protection circuits
RS485-Bus Electrical surge protection
Power supply Electrical surge and reverse current protection

Block and wiring diagram




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