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Case study 1,'Head of Queue' system

A customer was importing a ‘Head of Queue’ system for use in places such as banks, job centres, retail premises and the like. These consist of a unit at the head of a queue which advises customers when to go to a vacant serving position and an over counter number display to assist the customer in finding the free position. The counter staff press a call forward button at their station when ready to serve and this tells the head of queue which number to display.

The customer had a vision that if they could make a ‘Head of Queue’ system which used radio signals instead of hard wiring the system would be significantly cheaper to install and could be installed by persons with out electrical skills. Traditional systems require wiring from each call forwards button to the head of queue and from the head of queue to each over counter display meaning that to keep the shop environment tidy all the wiring has to be under-floor or in overhead spaces.

The design brief for the product was as follows:

  • Radio linked to minimise wiring.
  • Up to 64 counter positions to be catered for.
  • ‘Head of Queue’ to have voice messages, furthermore voice message to be selectable by counter staff to be male or female dependant on which button they pressed.
  • Battery life for over counter display and call forward buttons to be 1 year minimum.
  • System to be low cost.
  • No electrician wiring required.


Following the design brief Challenge Electronics was able to propose a design solution which offered the costs and benefits sought by the customer and a development and manufacturing program was started. The final product uses a radio transmitting key fob product as a call forward button and a single transmission is made when the button is pushed to minimise the battery usage. The head of queue unit monitors the radio frequency channel and when it detects a call forward it displays the counter number on a large custom LCD with direction arrows whilst playing the appropriate message ‘Please go to position 5’. Concurrently the head of queue also transmits on another radio frequency to the over counter units which wake up every 0.5s to check for their number and display, again on an LCD, when required. By the use of an LCD and the 0.5s wake up frequency battery usage in the over counter is also minimised and the target battery life is achieved.




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