Category Archives: Audio

Drive in movie

On the 7th of March we helped stage Fife’s first drive in movie! Lots of interesting stories to tell from the night but basically a huge success for all involved. The event was organised by Events students at Adam Smiths College with any profits going to CHAS.






2 films were shown, Toy Story for the family and later in the night Texas Chain Saw Massacre (2002). About 150 cars attended over two screenings, or should that be ‘truckings’? Yes the screen was the side of a truck provided by the organisers, unfortunately the promised white truck when picked it up had the hire companies logo on the side… Dooh! Thankfully we happened to have enough white material to cover part of the logo to make a reasonable screen area possible. It looks smaller in the picture due to the wide angle of the lens used… honest.

Sound was an interesting problem, normally such an event would be broadcast via FM radio, to be received by car radios, but the timings meant that there was not sufficient time to apply for a licence so a combination of IR transmission and Ch 70 radio was used. Each car was issued a receiver which was plugged into aux inputs or low power FM transmitters, designed to connect your mp3 player to your car radio.

The weather was a miracle, after gale force winds, snow and hail during the day the wind died and the sky cleared to perfect conditions through out the night!

Film goers showed their appreciation by massed tooting of horns after each performance. A memorable night which we are sure will be repeated.

Tour Guide Systems

We now stock ‘Listen’ Tour Guide systems. These can be used to to provide a guided tour with out the guide having to raise their voice to reach their audience. Very useful with a larger tour or in noisier environments. They are also especially suited to providing a single channel of one way interpretation for small groups.

Transmitter and head worn microphone

Our systems are packaged in a sturdy flight case in sets of 10 units. The guides / interpreters transmitter belt pack (and microphone) is presented in a separate tray as are the delegate receivers and head phones. This allows you to present the system in clean boxes out side of its road case so giving the best of impressions.

Tour Guide Case

We use the ‘Listen’ system over others available as you have the flexibility of different battery types, headset combinations for the delegates and microphone types for the guide / interpreter. The Transmitter belt pack can also take an audio signal from an iPod, or other audio device, allowing the delivery of pre recorded material. We chose to use dry cell batteries on these systems as it allowed us to make our own cases and also removed the complexity of having to recharge batteries for the user.

Delegate Receivers

Making our own cases was important to us as we found that the manufacturer supplied cases are normally nothing more than a dust cover and in our busy rental department we found such flimsy cases where getting badly damaged when transported by courier. The trays also allow you to place the receivers at your congress reception with out also displaying a road case covered in courier stickers! Available to hire from £100 + Vat  per day. Please contact us for more details and quotation.

 Click here to download our Quick Guide

Click here to download full system manual


New wireless delegate microphones soon to arrive.

AVD are pleased to announce that it is adding two new wireless delegate microphone discussion systems to its rental stock. The new systems will allow clients to use delegate ‘push to talk’  microphones with out the hassle and trip hazard of ugly cables.

Confidea wireless microphones

No messy wires…! Nice!

The new systems give delegates attending a full discussion meeting the ability to quickly and easily access the floor to make comment or to respond to questions with out waiting for a traditional hand held radio microphone to be passed round. They will also greatly reduce set up and strip out times allowing faster room turnarounds.

The initial deployment will see 2 systems enter stock complete with controller / access points and a chairmans unit. The two systems will also be capable of being combined to form one larger system. Each system comes in a bespoke flight case housing 12 wireless delegate microphone units, battery chargers and an access point.

AVD expect demand will be high as currently these systems are mainly held in stocks south of the boarder which can increases the cost of rental due to shipping as well as the limitation on short notice hires. AVD believe this will be the first such system to be held in stock and available to hire in Scotland. The new systems will be available for both serviced and dry hires as well as being added to our sales portfolio…

To book a demo, get more information and obtain a quotation contact us now…



What is a discussion microphone? Part 2

What is a discussion microphone? How is it different from a conventional microphone?  Part 2. Mark Kisby continues his explanation… (missed Part 1? click here)

Conference, discussion or ‘push to talk’ microphones provide the best conference audio solution for speech reinforcement. Though sometimes not the best in absolute sound quality, it is the ability for the microphone to be controlled by both delegate and sound technician that ensures every word is heard.

Boardroom discussion microphones

Discussion microphones set for a boardroom style conference

For this reason conference microphones are particularly suited to the recording of meetings, councils and parliaments and the provision of the ‘original’ feed to a simultaneous interpretation system.

In these applications the aims is to have as few microphones ‘live’ or ‘on’ at any one time, each ‘live’ microphone adds more back ground noise to the audio feed.

The standard operation of a sound desk with just 6 conventional microphones on a top table is to leave all 6 microphones live (but set to a low volume) so if someone does speak the technician need only increase the level of a microphone. This allows at least some audio, albeit low level to begin with, to be heard which is better than nothing. This is because the technician does not know who is going to speak next and the speaker is unable to make their microphone live independently of the technician. There are two main reasons why this is not acceptable in a recording or for simultaneous interpretation.

Firstly the delay in a delegate speaking and in the microphone becoming live, as the technician recognises which microphone is in use and increases its level,  introduces a pause into which whole sentences can disappear and critical meaning can be lost. Conference microphones can be operated by the speaker directly so eliminating this delay in making the microphone live or louder. This allows a freer flow of dialogue to take place without a word being lost. This is critical in the recording of important meetings and in the original language feed for simultaneous interpreters.

Secondly by having so many partially live microphones live you are introducing unwanted and distracting background noise into the audio. This is often not recognised by the delegates or by the technician who generally listen to the audio via the PA in the room where these noises are already present. However other users, e.g. interpreters, listen to the proceedings via headphones so they are very ‘close’ to the audio and can clearly hear the rustle of paper or the pouring of water. This unwanted audio is very distracting and can mask important elements of the speech.

With a conference microphone system you have the capability to control and help eliminate these spurious sounds without losing the critical audio by only having one or two microphones live at any one time.

The other added advantage is that it is possible for a system to extend to include  10 – 100 – 1000 participants so making the discussion microphone ideal for use in council chambers, parliaments and general meeting rooms.

The advantages in using discussion microphones or discussion systems are very clear (especially the audio!).

What is a discussion microphone?

What is a discussion microphone? How is it different from a conventional microphone? Mark Kisby explains… Now updated on the 6th of June 2017, please see additional text at the bottom of the post.

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.

Discussion Microphone

A discussion microphone also known as a ‘delegate’ or ‘conference’ microphone.

What makes a discussion microphone different to a conventional microphone is 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.

Boardroom discussion microphones

Discussion microphones set for a boardroom style conference

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.

Update. 6-6-17

Since originally writing this post over 6 years ago technology has moved on and the pro audio description and definition of some of the terms used to describe a system have become more specific. These can be set out in the following definitions.

Discussion Microphones.
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, it has no other features other than the microphone, a speak button and an integrated speaker.

Conference Microphones.
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.
  • Messaging
  • 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.