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Indactic 21

DOWNSupported Information Types
DOWNProtocol Features
DOWNImplemented Protocol Stacks
DOWNApplicable Products

The Indactic 21 protocol was developed in the eighties by the BBC company (today ABB) in order to connect their RTUs and SCADA systems. Indactic 21 encodes the data in a proprietary PCM code. It uses a synchronization signal with a pulse of 1.5 length (i.e. 1.5 / baud rate) to ensure unambiguous recognition of the telegram start. In practice baud rates between 200 and 600 Baud are used. And although these baud rates are quite low, the data volumes transmitted can be relatively large, as the encoding is not burdened with unnecessary information.

There are several protocol dialects, so the actual function scope may vary.

Spontaneous transmission of information changes by a substation without an explicit request or polling by the master is quite rare.  Additionally, the positive summary acknowledgment is applied, where the master acknowledges all telegrams received in the meantime in regular specified intervals in one go.


7 Application Layer Indactic 21 Application Layer
6 Presentation Layer n/a
5 Session Layer n/a
4 Transport Layer n/a
3 Network Layer n/a
2 Link Layer n/a
1 Physical Layer RS232 / V.24 (PCM)

Supported Information Types

Control Direction Double Command
Monitoring Direction Single indication [1 Bit]
Double indication [2 bit]
Measured value [8 bit] unipolar
Measured value [8 bit]
Measured value [9 bit]
Measured value [11 bit]
Tap position BCD
Counter value dual [8 bit]
Counter value dual [16 bit]
Counter value dual [32 bit]

Protocol Features

Physical Layer RS232 / V.24 (PCM) PtP
Application Layer Transmission of pulse commands
Spontaneous transmission of Indications, Measurands and Counters
General Interrogation
Grouped interrogation of Indications, Measurands or Counters
Address Space Station Address: 1..127
Information Type: as defined in protocol description
Group Address: 0..127

Implemented Protocol Stacks

Indactic 21, Master

Applicable Products

ipConvipConvUniversal protocol converter for highest degree of flexibility


Interconnection BAGZV, EWAGInterconnection BAGZV, EWAG
GermanyipConv Indactic 21, Master / IEC 60870-5-101, Slave /
RWE EllerRWE Eller
GermanyipConv Indactic 21, Master / IEC 60870-5-101, Slave /
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