The rear mounted buzzer... Do they conform? For many years rear mounted buzzers, incorporated into universal towing electrics have been used on vehicles by way of informing the driver in regard to the functioning of an indicator lamp on the trailer. When a trailer is connected and the indicators are operated these units will "beep" to inform the driver that the trailer lamp is functioning.

There is a great deal of mis-information surrounding these monitoring devices. Much of this has been circulated by those involved in the towing industry, It is assumed that the use of the rear mounted buzzer conforms to towing law, when in fact they do not.

“What is this law and what does it say?”

There are currently 3 European countries who have adopted the need for a tell-tale warning to monitor the trailer flashers. These are:  

• Germany  
• Austria  
• UK (incl N. Ireland, Channel Islands)

In actual fact, under EU law, every EU country which have vehicles that are equipped with towbars, should have a monitoring system for the trailer flashers, but it has been decided that certain country specific requirements and local law, have been observed and therefore chosen not to adopt this function. The 3 countries named above have always adopted and conformed. It is important to point out that the subject of tell-tales is still very much in discussion and pressure is still on EU countries to conform. After extensive research, it was clear that the monitoring of trailer indicators is concise. The relevant laws in respect of tell tale devices is titled 'ECE Regulation 48' and also includes the UK’s Construction & Use regulations 1986 (no link available). Both laws concern the 'Approval of vehicles with regard to the installation of lighting and light signaling devices'. So, in effect, they control all lighting requirements on vehicles & trailers, how they are positioned and monitored and what tell-tale and/or warning devices should be fitted. It was drawn up and agreed in November 1981. The Construction & Use regulations became law in 1986. The section that applies to the monitoring of the trailer flashers is found in section 6.5.8 of R-48 and the relevant paragraphs from the directive are shown below:

“EC R-48 Lighting & Lighting Devices 1981”

"6.5.8 
Tell-tale Operating tell-tale mandatory for front and rear direction indicator lamps. It may be visual or auditory or both. If it is visual it shall be a flashing light which, at least in the event of the malfunction of any of the front or rear direction indicator lamps, is either extinguished, or remains alight without flashing, or shows a marked change of frequency (double speed flash). If it is entirely auditory it shall be clearly audible and shall show a marked change of frequency, at least in the event of the malfunction of any one of the direction indicator lamps.
If a motor vehicle is equipped to draw a trailer, it must be fitted with a special visual operational tell-tale for the direction indicator lamps on the trailer unless the tell-tale of the drawing vehicle allows the failure of any one of the direction indicator lamps on the vehicle combination thus formed to be detected.”

The first part of paragraph 6.5.8, details the requirements for general vehicle indicator monitoring. It is the second half which sets the requirements for monitoring the trailer flashers. The UNECE R-48 law states that if a vehicle is equipped to draw a trailer, it must be fitted with a special visual tell-tale to monitor the trailer indicators. This can be either a separate lamp which can be installed in the dash, or the use of a built-in lamp fitted in the dash display. There is no mention of an audible monitor. UK law allows an audible to be accepted. Secondly, this visual tell-tale is to be fitted UNLESS the vehicle is able to monitor the trailer indicators using it's own direction indicator tell-tales. The final, most important requirement is that the tell-tale system MUST monitor failure of all or any of the indicators on the combination. This means the driver has to be informed of any failure of both the car and trailer indicators! The standard rear buzzer installation will NOT do this.

"What about the UK Construction & Use regulations 1986?"

Below is an extract from the C&U regulations for the UK, which covers the requirements of tell-tales for indicators. Paragraph 11 stresses that the tell-tale is not specifically visual, so audible monitoring is quite acceptable, but it still needs to monitor ALL the indicators. You will notice also in paragraph 12 that there is still the requirement for the driver to be aware of failure of any of the indicators from the towing vehicle or the trailer:

"11. Tell-tale- (a) One or more indicators on each side of a vehicle to which indicators are fitted shall be so designed and fitted that the driver when in his seat can readily be aware when it is in operation; or (b) The vehicle shall be equipped with an operational tell-tale for front and rear indicators (including any rear indicator on the rearmost of any trailers drawn by the vehicle). 

12. Other requirements- (a) Every indicator (other than a semaphore arm, that is an indicator in the form of an illuminated sign which when in operation temporarily alters the outline of the vehicle to the extent of at least 150 mm measured horizontally and is visible from both the front and rear of the vehicle) shall when in operation show a light which flashes constantly at the rate of not less than 60 nor more than 120 flashes per minute. However, in the event of a failure, other than a short-circuit of an indicator, any other indicator on the same side of the vehicle or combination of vehicles may continue to flash, but the rate may be less than 60 or more than 120 flashes per minute. Every indicator shall when in operation perform efficiently regardless of the speed of the vehicle. (b) Where two front or rear direction indicators are fitted to a motor vehicle first used on or after 1st April 1986, and two rear direction indicators are fitted to a trailer manufactured on or after 1st October 1985, in each case they shall be fitted so as to form a pair. (c) A rear direction indicator on each side of a vehicle shall not be fitted on a boot lid or other movable part of the vehicle."

Extract from: Statutory Instrument 1989 No. 1796 The Road Vehicles Lighting Regulations 1989 - Schedule 7 part 1: Para 11 & 12

The design of the rear mounted buzzer

They are designed to be joined in “series” onto the vehicle's indicator lamp circuit. Principally then, when the trailer plug is pushed into the towing socket and an earth circuit is made, with the direction indicator operating on the vehicle, a signal is passed through the buzzer unit, and the buzzer will sound in unison with the flash rate of the vehicle. If the bulb fails on the trailer, the circuit is broken, and the buzzer will stop sounding. The installation of this device is simple and they can be purchased very cheaply.

The rear mounted buzzer - why they do not conform.

Most vehicles will have a flasher system designed to control 2x 21w + 1x 5w per side, with a constant flash rate. This is either with a flasher unit or with a frequency control unit incorporated into the central electrics. The vehicle is designed in principal to 'count' the number of bulbs per side, and report a fault if the resistance drops below a minimum preset threshold, meaning a bulb has blown. When a trailer is connected, and a rear mounted buzzer is fitted, the vehicle will now 'count' 4 bulbs per side, and the resistance of the circuit will have risen. The buzzer will operate as usual, but should a front flasher bulb fail on the vehicle, the vehicle reverts back to counting the resistance of 3 bulbs (the side repeater, the rear on the vehicle, and the trailer bulb). This means the resistance does not drop below the lower threshold level and therefore there is no change in the flash rate cycle. The driver WILL NOT be informed of this failure.

THIS FUNCTION DOES NOT CONFORM TO THE LEGAL REQUIREMENTS for monitoring either under paragraph 6.5.8 (highlighted) and C&U 11 (b) and paragraph 12. This type of installation can be potentially disastrous for the road user should the vehicle not be equipped with an active front flasher!

Alternative rear mounted buzzer

On certain vehicles with sensitive electronics or those that may have a bulb check control system, universal electrics will incorporate a module which acts as a by-pass and therefore remains hidden from the vehicle. A buzzer is often mounted on such a module and therefore should a flasher on the vehicle fail when towing, a double flash rate will be created even though the buzzer will still be sounding. This is because the car does not detect the flasher on the trailer. (This will conform to the law).

In Conclusion..

It is therefore VERY important that you choose an electrical installation that conforms to all legal requirements. Any towing product supplied by Right Connections will be equipped with a monitoring system that conforms absolutely to ECE R-48 & to the Construction & Use regulations for the UK.