What is a discussion microphone? How is it different from a conventional microphone? Mark Kisby explains.
Commonly referred to as a discussion microphone, delegate microphone, conference microphone, or Push to Talk. This type of microphone is used as part of a larger system of microphones where the use of a conventional microphone is impractical.
What makes a discussion microphone different to a conventional microphone is that typically a discussion microphone will have a built in pre-amp, this allows for an installation that ‘daisy chains’ the microphones in series and sending the audio along a common ‘bus’. The conventional microphone as used for music or recording has no pre-amp instead this is contained in a sound desk or mixer. This conventional arrangement requires individual cables to be run from the sound desk to each microphone. The discussion microphone is usually enclosed in a table top enclosure that houses the microphone, pre-amp, an on /off button, and possibly an amplifier with a small ‘personal’ speaker.
Both types have different applications, conventional microphones are used for music (both in live sound, recording) and in speech applications where individual tonal / gain controls are required. i.e. lectern or top table. Discussion microphones are used for situations of extended speech reinforcement applications ie. Conferences, Board rooms, Council Chambers, Parliaments, etc… With these applications in mind a discussion microphone system has features which are unique to its type.
Designed to allow the orderly control of a meeting, these features include:- Push to talk (PTT) on /off microphone activation switch to allow delegate operation. A microphone mounted light to show the microphones status, not only the user but also other delegates / chairman. A limit on the number of microphones that can be ‘live’ at any one time is applied, typically 6-8 microphones, to prevent too many microphones becoming live and causing feedback (howling speakers).
The limiter is normally adjustable to various modes of operation including ‘Automatic’ where delegates switch ‘on’ and ‘off’ their microphones at will. The ‘Manual’ mode is where delegates ‘request to speak’ and their microphone is made live by the chairman or a technician when it is their turn to speak. Another feature is the ability of a chairman’s or president’s microphone to over ride all others.
Discussion microphones connect via a ‘daisy chain’ cable network that puts the microphones in series running back to a central controller. The controller outputs a single audio connection which allows up to a hundred microphones to be connected to just a single audio input on a sound desk or amplifier. More modern digital systems may make use of common cable types such as Cat5, some systems may use a proprietary cable which is unique to the system and can add greatly to the cost of an installation.
The daisy chain cable arrangement suited the traditional table layouts of board rooms and council chambers however this has now developed in to wireless models which allow the use of these systems easily in a cabaret table style arrangement. Wireless systems also allow for the installation of such a system in a listed building where a cabled installation would be invasive or where a room needs to be multi purpose requiring the easy removal and re-installation of the equipment.
Control of the system is by a chairman’s unit or a comprehensive technicians control panel which allows full remote control of all microphones.
I hope this helps explain this type of microphone. Look out for another post soon on how these microphones are used in simultaneous interpretation systems.
The pro audio description and definition of some of the terms used to describe a system can be more specific.
A simple microphone discussion system only provides audio. i.e. it is only a microphone system and is limited to that function. It can provide the opportunity for a delegate to speak and it gives the chair person some elements of over ride and some queuing controls to maintain a procedure and order. It will allow connection to an external audio system for amplification and recording.
The above unit is a discussion microphone, generally it has no other features other than the microphone, a speak button and an integrated speaker.
A conference microphone is like a discussion microphone but with additional features to facilitate a conference or congress so it is not just the main audio source. A conference microphone may have some or all of the following additional features.
- Delegate identification via chip card or RFID
- Simultaneous interpretation with built in channel selectors and headphone sockets
- Audience response and voting
- Content and Agenda displays
- Wider technician control network
- Camera control
The phrase conference microphone when searched can still bring up everything from a single microphone as used in connection with video conferencing or tele conferencing systems to a full system as described above. I expect the definition of Conference Microphone to further develop and the term used to describe a complex conference microphone system to become a Congress Microphone System.
The unit above is a Conference microphone, it has the mic, speak button and the speaker of the discussion microphone but also a chip card reader for delegate ID, integrated touch screen that allows local display of agenda and provides voting buttons, headset volume control, interpretation channel selection. Etc…
Push To Talk Microphones (PTT)
This term is now largely exclusive to the type of microphone you would find connected to a two way radio transceiver of the type used on board a boat or CB radio. This is where you physically have to press, and hold, the button while talking. Releasing the button switches you off, releases the frequency and allows another to transmit. An announcement PA in a school may have a similar desktop version of a PTT microphone as shown below.
The user of a system may still refer to all the known terms (Push to Talk, etc..) in describing what they require, and it will be up to the supplier to drill down to the requirement and provide the needed solution. We are here to help in that regard.