Two-way Communication – The Classic Intercom Function

In one of our first blog posts, I gave an introduction to two-way communication, the most common type of voice connection used in Intercom systems (see Intercom and PA/GA). With this blog article, I want to provide more information on two-way communication.

Communication in Both Directions

A two-way connection provides communication in both directions (bidirectional) where both subscribers can speak and listen alternately, but not simultaneously. One subscriber speaks and the other listens. Only when the first subscriber has finished his message, the other can answer.

Direct Dial Key or Dial Keypad

A two-way connection to another subscriber can be established by pressing a direct dial key or by entering a call number using the dial keypad. The advantage of direct dial keys is that the connection to a pre-defined target can be established faster than entering the call number digit by digit. The advantage of dial keypads is that you can establish connections to any desired targets. So, all subscribers are able to speak to each other.

The illustration below shows the communication process by using a direct dial key.

In contrast to conventional telephony, there are no connection setup times. If the target is free and can be reached, a two-way connection is immediately established. For process communication, this means valuable time saving, e.g. if you need to quickly communicate instructions from the control room to the staff in a plant or on a platform. In steel mills, you often inform staff about the next process steps using short announcements such as “Empty the torpedo car!” or “Casting process starts!”. You can also draw people’s attention to potential dangers (“Caution! The crane moves!”).

Priorities

You can assign a priority for each two-way connection. This means that an active connection remains busy for other subscribers with the same or a lower priority. Connections with higher priorities can however interrupt the existing ones at any time to ensure that important information is broadcasted, e. g. alarms. The use of priorities is typical for advanced solutions in hazardous areas.

Remark

The term “two-way connection” is often abbreviated as “TW connection”. You will also often find the more technical term “half-duplex connection”.

0 thoughts to “Two-way Communication – The Classic Intercom Function

  • Mukesh Shah

    Often a customer has a question, what is the difference between a conventional telephone and the plant intercom? This article aptly answers one of the most important difference between the two.

    Reply
    • Marco Holzhäuser

      Dear Mukesh,

      thank you for your reply.
      There are even more differences between intercom and conventional telephony besides the ones I mentioned in the article.

      You can establish a voice connection to a group of subscribers also without having any connection setup times by easily pressing one key, for example.
      Another important point is when you place a call you can see in advance at a LED indicator if the target can be reached or if it is busy.
      Further, you can assign an individual priority for every voice connection. In telephony all subscribers are on the same priority level.

      There is also a wide range of appropriate intercom stations (call stations) for different industrial needs. Normal telephones are not designed for such harsh environments.

      Many greetings
      Marco Holzhäuser

      Reply

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