Indactic 21

  • 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

Available Protocol Stacks

Indactic 21, Master

Applicable Products
  • ipConv

    Universal protocol converter for highest degree of flexibility

  • Interconnection BAGZV, EWAG
    Interconnection BAGZV, EWAG, Germany

    Products: ipConv
    Protocol Stacks: Indactic 21, Master IEC 60870-5-101, Slave

  • RWE Eller
    RWE Eller, Germany

    Products: ipConv
    Protocol Stacks: Indactic 21, Master IEC 60870-5-101, Slave