| Description | Date | Identifier | |
| Instructing the stores to return a tested 'Clear Hoot Horn' to Comm. Briggs. | 17th Mar 1925 | Box 59 \ 3 Scan041 | |
| The return of a 'Clear Hoot Horn' to a customer. | 17th Mar 1925 | Box 59 \ 3 Scan042 | |
| From R. to C. discussing the relative irritation of different car horns like the klaxon and vibrator. | 20th Apr 1925 | Box 59 \ 3 Scan043 | |
| The return of an unsuitable Autovoce horn. | 28th Oct 1925 | Box 59 \ 3 Scan044 | |
| Order for a Boa Constrictor Bulk Horn with a nickel finish for the 12-EX Phantom car. | 21th Apr 1926 | Box 59 \ 3 Scan045 | |
| Sales proposition for a three-horn setup, expressing disapproval of the idea and the necessary change-over switch. | 30th Apr 1926 | Box 59 \ 3 Scan046 | |
| To the Experimental Department regarding the tone of a horn from Clear Hooters Ltd. | 29th Apr 1927 | Box 59 \ 3 Scan047 | |
| Letter from Clear Hooters Ltd. regarding the dispatch, features, and pricing of a 'Clear Hooter' car horn. | 27th Apr 1927 | Box 59 \ 3 Scan048 | |
| Communication regarding a delayed shipment of a Cobra horn for the 18-EX Experimental Saloon. | 30th Nov 1923 | Box 59 \ 3 Scan049 | |
| Change from Klaxon rotary horns to buzzer-type horns, evaluating Robert Bosch and Sparton models. | 3rd Mar 1929 | Box 59 \ 3 Scan050 | |
| Instructions and specifications for a Klaxon Buzzer-Type Horn. | 22th Mar 1929 | Box 59 \ 3 Scan051 | |
| Technical notes on the construction and performance characteristics of an electric horn. | 8th Dec 1924 | Box 59 \ 3 Scan052 | |
| Instructions regarding the operation and mounting of the Sparton horn. | 8th Dec 1924 | Box 59 \ 3 Scan053 | |
| Missing special two-way switch for a Klaxon 2-tone horn. | 5th Apr 1929 | Box 59 \ 3 Scan054 | |
| Urgent internal order for a Bosch horn for Mr. Royce's car. | 6th Jun 1929 | Box 59 \ 3 Scan055 | |
| Requesting the procurement of a 2-note Bosch horn for comparison with a single-note horn. | 7th Jun 1929 | Box 59 \ 3 Scan056 | |
| Consignment note from Eural Patents Ltd to Rolls Royce Ltd for a Jubilee horn and a fitting. | 7th Jun 1929 | Box 59 \ 3 Scan057 | |
| Instruction sheet describing the R Bosch Horn U.K. 12. | 12th Jun 1929 | Box 59 \ 3 Scan058 | |
| Instructions detailing the electrical characteristics and operational parameters of a horn. | 1st Dec 1924 | Box 59 \ 3 Scan059 | |
| Instructions regarding the sound, pitch, and installation of a vehicle horn, comparing it to Klaxon and Sparton models. | 8th Dec 1924 | Box 59 \ 3 Scan060 | |
| Fitting of a Robert Bosch Horn, Type U.K.12, to a 20 HP chassis. | 1st Jul 1929 | Box 59 \ 3 Scan061 | |
| The unsatisfactory testing of two makes of vibration type electric horns. | 6th Jul 1929 | Box 59 \ 3 Scan062 | |
| Testing two sample Lucas buzzer type horns against the performance of the Bosch type. | 2nd Jul 1930 | Box 59 \ 3 Scan063 | |
| Request to test a 12-volt No.109 Wind Horn submitted by Klaxon Limited. | 22th Jul 1930 | Box 59 \ 3 Scan064 | |
| Test report on the Klaxon Wind Horn No. 109, concluding it is too blatant and noisy for use. | 23th Jul 1930 | Box 59 \ 3 Scan065 | |
| Sending a sample High Frequency Horn (instrument no. 17579) submitted by Klaxon Ltd for testing. | 25th Jul 1930 | Box 59 \ 3 Scan066 | |
| Options for sourcing or manufacturing a new electric horn to replace the standard Klaxon. | 26th Aug 1930 | Box 59 \ 3 Scan067 | |
| Cover note for an attached letter from The Klaxon Co. about Klaxon horns having a similar tone to Bosch horns. | 8th Sep 1930 | Box 59 \ 3 Scan068 | |
| Letter from Klaxon Limited regarding the development and testing of warning signal instruments. | 22th Sep 1930 | Box 59 \ 3 Scan069 | |
| Comparison of Lucas & Bosch buzzer type horns. | 22th Sep 1930 | Box 59 \ 3 Scan070 | |
| Comparison and analysis of a Lucas buzzer horn against a Bosch horn. | 10th Sep 1930 | Box 59 \ 3 Scan071 | |
| Comparison and analysis of the Lucas horn against the Bosch horn, detailing construction, adjustments, and performance. | 10th Sep 1930 | Box 59 \ 3 Scan072 | |
| Comparison of the construction differences between Bosch and Lucas horns, focusing on the disc, base, and mounting. | 30th Sep 1930 | Box 59 \ 3 Scan073 | |
| Specifications and test notes for a Klaxon Buzzer Horn (Bosch type). | 30th Sep 1930 | Box 59 \ 3 Scan074 | |
| The specifications and testing of a Klaxon Buzzer Horn (Bosch Type). | 2nd Oct 1930 | Box 59 \ 3 Scan075 | |
| Confirming there is no record of a Lucas Electric Horn being delivered to the Works or the Experimental Department. | 5th Nov 1930 | Box 59 \ 3 Scan076 | |
| Letter to Klaxon Ltd. requesting an update on the development of a buzzer-type horn to replace the current standard motor-type horn. | 5th Nov 1930 | Box 59 \ 3 Scan077 | |
| Letter from Klaxon Ltd. regarding a sample instrument, a new order, and its superior audibility compared to a foreign model. | 6th Nov 1930 | Box 59 \ 3 Scan078 | |
| Letter from Klaxon Limited requesting performance feedback on a sample horn being tested and confirming two more will be sent. | 6th Nov 1930 | Box 59 \ 3 Scan079 | |
| Ordering two Klaxon Buzzer Type Horns and deferring a performance report to Klaxon Limited. | 7th Nov 1930 | Box 59 \ 3 Scan080 | |
| Confirming that two Buzzer type instruments from the Klaxon Co. have been received and sent to the Experimental Dept. | 18th Nov 1930 | Box 59 \ 3 Scan081 | |
| Customer dissatisfaction with a new Klaxon horn, delaying its standardization. | 19th Nov 1930 | Box 59 \ 3 Scan082 | |
| The bench testing of two Klaxon buzzer horns, models S.21098 and S.21099, for cars. | 21th Nov 1930 | Box 59 \ 3 Scan083 | |
| Providing negative feedback on a two-note Klaxon horn. | 21th Nov 1930 | Box 59 \ 3 Scan084 | |
| The fitting of a vibrator horn and discussion of Klaxon versus Bosch horns for chassis 58-GN. | 21th Nov 1930 | Box 59 \ 3 Scan085 | |
| The search for a suitable English-made two-note horn and the assessment of a rejected sample from Klaxon. | 24th Nov 1930 | Box 59 \ 3 Scan086 | |
| Request to send a two-note klaxon horn for examination and potential improvement suggestions. | 25th Nov 1930 | Box 59 \ 3 Scan087 | |
| Dispatch of a sample two-note Klaxon horn and its ownership status. | 26th Nov 1930 | Box 59 \ 3 Scan088 | |
| Selection of a two-note electric horn, comparing Bosch and Klaxon models. | 27th Nov 1930 | Box 59 \ 3 Scan089 | |
| Sending of a Bosch horn to be fitted for trial. | 27th Nov 1930 | Box 59 \ 3 Scan090 | |
| Replacement of existing horns on Phantom II and 20/25 HP chassis with a new English manufactured horn. | 1st Dec 1930 | Box 59 \ 3 Scan091 | |
| Instruction sheet detailing the testing and characteristics of a Klaxon two-note horn, model S20774. | 2nd Dec 1930 | Box 59 \ 3 Scan092 | |
| Requesting the return of a 'Bosch' horn belonging to another car. | 2nd Dec 1930 | Box 59 \ 3 Scan093 | |
| Design of a new dual-note electric horn, combining Bosch and Cobra horn notes. | 4th Dec 1930 | Box 59 \ 3 Scan094 | |
| Requirements and specifications for single and two-tone Klaxon buzzer type horns for different chassis. | 8th Dec 1930 | Box 59 \ 3 Scan095 | |
| Technical analysis comparing the tonal qualities and harmonics of Klaxon and Bosch car horns. | 8th Dec 1930 | Box 59 \ 3 Scan096 | |
| Cover memo for a report on Klaxon buzzer type horns, requesting feedback on road experience. | 9th Dec 1930 | Box 59 \ 3 Scan097 | |
| Replacing the Klaxon horn on the P.2. and 25HP models with a more cost-effective alternative. | 11th Dec 1930 | Box 59 \ 3 Scan098 | |
| Required sound penetration of single and two-tone Klaxon buzzer type horns for touring safety. | 11th Dec 1930 | Box 59 \ 3 Scan099 | |
| Requesting an opinion on a 'Bosch' horn to establish a standard for the vibrator instrument. | 17th Dec 1930 | Box 59 \ 3 Scan100 | |
| Comparing the performance of Bosch and Klaxon car horns, concluding the Bosch is unsuitable for standardization. | 22th Dec 1930 | Box 59 \ 3 Scan101 | |
| Evaluation of Bosch and Klaxon buzzer type horns, proposing to fit a preferred Bosch model for testing. | 2nd Jan 1931 | Box 59 \ 3 Scan102 | |
| Querying the retention of a 2 Note Horn from Klaxon Ltd. to enable payment of the invoice. | 2nd Jan 1931 | Box 59 \ 3 Scan103 | |
| Trial of a Buzzer Type Bosch horn, noting a difference from a newer model. | 1st Jan 1931 | Box 59 \ 3 Scan104 | |
| Instruction to send the latest type Bosch buzzer horn, model UK.12A. | 1st Jan 1931 | Box 59 \ 3 Scan105 | |
| Despatch of a Bosch Buzzer Typehorn for trial. | 7th Jan 1931 | Box 59 \ 3 Scan106 | |
| Harmonic tests of buzzer type horns. | 9th Jan 1931 | Box 59 \ 3 Scan107 | |
| Trial of a Bosch UK.12A horn and concluding against replacing the Klaxon horn. | 15th Jan 1931 | Box 59 \ 3 Scan108 | |
| Letter from Klaxon Limited regarding the development of a more distinctive warning horn for Rolls Royce cars. | 10th Feb 1931 | Box 59 \ 3 Scan109 | |
| Short note from Klaxon Ltd to Mr. Clarke with a waveform analysis of a horn supplied to RR. | 11th Feb 1931 | Box 59 \ 3 Scan110 | |
| Return of a Klaxon Buzzer Type Two Note Horn for credit. | 1st Mar 1931 | Box 59 \ 3 Scan111 | |
| Letter to Messrs. Klaxon Ltd. apologising for a delay in replying and advising of ongoing laboratory work. | 10th Mar 1931 | Box 59 \ 3 Scan112 | |
| Inquiry to Klaxon Ltd. regarding the development progress of a new high-frequency buzzer horn. | 1st Jun 1931 | Box 59 \ 3 Scan113 | |
| Letter from Klaxon Ltd. discussing difficulties in producing a new instrument sample and the unsuitability of the current model. | 4th Jun 1931 | Box 59 \ 3 Scan114 | |
| Letter to Lucas Electrical Co. Ltd. regarding the failure of a Lucas Alto Horn and requesting trial samples of improved models. | 15th Jun 1931 | Box 59 \ 3 Scan115 | |
| Failed Lucas Alto Horn being sent to The Lucas Electrical Co. Ltd. | 5th Mar 1931 | Box 59 \ 3 Scan116 | |
| Letter chasing Lucas Electrical Co. Ltd for replies regarding windscreen wipers and horns. | 26th Jun 1931 | Box 59 \ 3 Scan117 | |
| Instructions for fitting a Lucas Alto Horn type HF.43 No.53 to chassis 20-EX for testing. | 6th Jul 1931 | Box 59 \ 3 Scan118 | |
| Letter from Joseph Lucas Limited concerning the supply and specifications of HF.43, Alto, and Altette horns, and a new windscreen wiper. | 8th Jul 1931 | Box 59 \ 3 Scan119 | |
| Letter from Joseph Lucas Ltd. explaining the cause of a fractured guide spring on a type HF.43 Alto Horn due to an incorrectly assembled washer. | 1st Jul 1931 | Box 59 \ 3 Scan120 | |
| Letter to Joseph Lucas Ltd. regarding the trial of a replacement car horn on a Phantom II chassis. | 6th Jul 1931 | Box 59 \ 3 Scan121 | |
| Testing and proposed fitting of new H.F. type electric horns from Lucas. | 9th Jul 1931 | Box 59 \ 3 Scan122 | |
| Request to manufacture two brackets to fit a grille type electric horn to the front dumb iron of a chassis. | 11th Jul 1931 | Box 59 \ 3 Scan123 | |
| Request to order a Lucas horn push switch for testing, with a preference for a steering column fitting. | 7th Aug 1931 | Box 59 \ 3 Scan124 | |
| Return of a Lucas H.F. Alto horn for modification and testing. | 9th Aug 1931 | Box 59 \ 3 Scan125 | |
| Request to fit an H.F. type Lucas Alto electric horn to chassis 18-GIV for comparison with the existing Klaxon horn. | 20th Aug 1931 | Box 59 \ 3 Scan126 | |
| Letter to Lucas Electrical Co. Ltd. regarding the testing and investigation of an Alto horn for use on an R.R. chassis. | 25th Aug 1931 | Box 59 \ 3 Scan127 | |
| Requirement for a dash-fixing horn push switch for a Lucas Alto H.F. Horn. | 27th Aug 1931 | Box 59 \ 3 Scan128 | |
| Confirming the suitability of a Lucas Horn Button push switch. | 28th Aug 1931 | Box 59 \ 3 Scan129 | |
| Recommending the sale of a discarded Lucas 'Alto' horn to an employee for 15 shillings. | 9th Sep 1931 | Box 59 \ 3 Scan130 | |
| Invoiced Alto Horn from supplier Joseph Lucas, Ltd. and how to proceed with the debit. | 6th Oct 1931 | Box 59 \ 3 Scan131 | |
| Fitting and payment for a Lucas Alto Horn HF.415 on an experimental chassis. | 9th Oct 1931 | Box 59 \ 3 Scan132 | |
| Letter to Joseph Lucas Ltd. regarding the testing of their Alto grille type horn and windscreen wiper. | 29th Dec 1931 | Box 59 \ 3 Scan133 | |
| Lucas representative taking a high frequency horn and a windscreen wiper for repair. | 1st Jan 1932 | Box 59 \ 3 Scan134 | |
| Proposal for fitting an electric H.F. horn to vehicle 20-GIV. | 9th Dec 1931 | Box 59 \ 3 Scan135 | |
| Confirming the decision to keep the Klaxon horn after trials and requesting an official order be placed. | 4th Dec 1931 | Box 59 \ 3 Scan136 | |
| On the successful testing of a Lucas high-frequency horn and its proposed fitment on a 20/25 car. | 3rd Jan 1932 | Box 59 \ 3 Scan137 | |
| Request to obtain a 12-volt Bosch medallion type horn for testing on a 10,000-mile test car. | 3rd Jan 1932 | Box 59 \ 3 Scan138 | |
| Various electric horn options for the J. 3 model. | 13th Jan 1932 | Box 59 \ 3 Scan139 | |
| The placement of a high-frequency electric horn to meet sales requirements. | 15th Jan 1932 | Box 59 \ 3 Scan140 | |
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