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“Roger W. Riehl and the Synchronar: World’s First Solar-Powered Wristwatch”

The world’s first solar-powered wristwatch was invented by a self-taught electronics expert named Roger William Riehl. The name he coined for the solar-powered wristwatch was Synchronar (also referred to as the Synchronar 2100) Riehl rationalized the name (acronym) of Synchronar from: SYNchronous CHRONometer calendAR. Riehl built and tested prototypes from the late 1960s into the early 1970s and the first production model was released in 1972. After the Synchronar was released Riehl worked on innovative improvements to the original design for the rest of his life. Over a span of 33 years Riehl designed and released a total of four models of his Synchronar wristwatch: Mark I, II, III and IV, and a less expensive version called the Sunwatch. The cases were made available in a variety of materials: stainless steel, black ceramic, solid gold, gold plating, rhodium plating and titanium.

Riehl was born on Christmas day, December 25, 1935, in Brooklyn, New York and died on February 16, 2005 in New Berlin, New York.

An Electronics Expert From an Early Age

From an early age Riehl was interested in electronics and gadgetry in general. He demonstrated an aptitude for electronics when he taught himself how to repair television sets at the age of 11. At the age of 15 he designed and built a pinball machine in the basement of his parent’s house which won the 1950 9th grade grand prize at the 3rd annual Herkimer Science Congress at North School in Herkimer, New York.

At age 16 he designed and assembled an electronic football field scoreboard that was made from junk and discarded parts that included old electric train transformers, six soup cans, damper motors from heat control systems, wire from coin machines and a curtain rod. This feat won him a first prize in the 1952 Whitesboro Central School physics competition.

At age 18 he wrote a paper titled, “The Electronic Regulation of the Audible Spectrum.” This paper and his demonstration of equipment which included a record player, electrical meters and vacuum tubes won the grand prize in the Chemistry-Biology-Physics contest at Whitesboro Central School in 1953. He also participated (in 1952 and 1953) in the State Science Congress sponsored by the New York State Science Teachers Association for Future Scientists of America.

The Many Paths of Roger W. Riehl

In adulthood Riehl became a self-taught engineer who was able to visualize and conceptualize new electronic devices, and possessed the uncanny ability to design and invent them without a formal engineering education.

Riehl honed his electronic and design skills at various companies before taking on the personal challenge of designing and constructing a digital solar-powered wristwatch.

From 1954 to 1957 he worked as a television repairman and built custom hi-fi sound systems in the Utica, New York area.

In 1958 he moved to Cincinnati, Ohio and worked at a cousin’s television appliance business as a television repairman.

It was in 1959 that he first got the idea for a digital solar-powered wristwatch after he realized how military devices were utilizing integrated circuits (ICs).

In 1960 he worked at the Dayton Aviation Radio Equipment (DARE Electronics, Inc.) as an engineer working on 2-way FM radio development. While at DARE he flew worldwide as a flight crew member testing navigation equipment for Air Force and Naval applications. He also obtained the FCC Second Class Technical license in 1960.

He started a company called Riehl Engineering in 1960 working out of a room in his home. It was here that he first started working on his idea to design a digital solar-powered wristwatch device. He also designed and marketed a transistor ignition system called Spitfire This device claimed to keep an automobile engine in proper timing (up to ten times longer), and to increase horsepower by 20%.

Throughout the mid to late-1960s he explored many ideas related to solar power devices and how to design a wristwatch with wire filaments and an electronic digital display that would work by storing energy in a solar cell.

He operated Riehl Engineering until late in 1964. Then, in 1965 he opened the Riehl Electronics Corporation (REC) in an industrial building in Troy, Ohio. This company made and distributed various electronic products including the MagneTach Tachometer/Dwell Meter, and heat sinks.

Riehl was also busy working on his solar-powered wristwatch concept and was able to complete various prototypes (during the period from 1968 to 1972). Prototypes, and the production models, did not look like traditional wristwatches (other than they strapped onto the wrist) as they had a “Space Age” appearance which made the concept even more revolutionary.

From 1969 through 1970 he worked as an Electronics Engineer at Hobart Manufacturing in Dayton, Ohio. It was here that he was instrumental in the design of the world’s first digital delicatessen scale. A United States Patent was granted (US3741324 A - weighing scale with digital display). He continued to work on his designs and testing of his digital solar-powered wristwatch concept in addition to his responsibilities at Hobart.

In 1970 he returned full-time to the Riehl Electronics Corporation to bring his dream of a digital solar-powered wristwatch to reality. In 1971 Riehl began selling stock in the Riehl Electronics Corporation to fund the digital solar-powered wristwatch project. He filed for a United States Patent on May 3, 1971 (US 3823551 A – Solid State Electronic Timepiece).

From late 1971 to early in 1972 Riehl completed a working prototype of a digital solar-powered wristwatch that included two revolutionary slider control switches on the top of the case. This slider control design passed all of his intense water-proof testing and was soon ready to be released for sale to the public.

The Synchronar is Released and the Struggles to Keep it in Production

Later in 1972 Riehl completed the world’s first production-ready digital solar-powered wristwatch that featured custom state-of-the-art complementary metal-oxide semiconductor (CMOS) circuits that he designed.

The introduction of the Synchronar proved that the world’s first digital solar-powered wristwatch was not just a “Space Age” aberration it was a challenge to the mainstream traditional wristwatch designs of the 1970s.

The first Synchronar production wristwatches were made at Riehl Electronics Corporation in Troy, Ohio. Ness Time marketed most of the first production Synchronar wristwatches during 1972 and into 1973. They were tasked with finding a CMOS circuit manufacturer in the Silicon Valley area of California, but could not contract one. Riehl decided to sever the partnership with Ness Time and worked with Ragen Semiconductor, a subsidiary company of Ragen Precison, who became the sole supplier of the unique CMOS circuits.

Additionally, Riehl sold some of his earliest watches to the Hammacher Schlemmer store in New York, NY and many were marketed through their mail order catalog.

The Synchronar is a very unique wristwatch, and remains a futuristic curiosity even today. The top of the watch looks similar to a cobra’s head and houses a silicon solar cell. The time is displayed in red digits by a light emitting diode (LED) display on the side of the watch. The design of the watch was so revolutionary that the Riehl Electronics Corporation filed for a United States Patent on November 6, 1973 (Des. 229,085 – Wristwatch).

In 1974 Riehl joined Ragen Semiconductor, Inc. in Whippany, New Jersey as the Vice-President of Operations (for the Synchronar Solar-Powered Wristwatch product). Riehl became President in 1975. Starting in 1974 and continuing into 1976 Ragen Semiconductor manufactured and marketed the Synchronar. During this time the Mark I and Mark II (released in 1975) models were produced. The Mark II model had additional features that included a digital frequency synthesizer which increased its accuracy (the frequency could be adjusted by the user with magnets.)

To prove the versatile and rugged nature of the Synchronar, Ragen Semiconductor included a Performance Certification with all of their watches. This stated that the Synchronar will normally survive the following tests: Pressure Cook: 24 Hours in salt brine @ 60º C, Salt Spray: Salt Water Spray for 100 Hours, Trip Hammer: 1000 Drops 1 foot onto a Marble Slab, Oven Bake: 100 Hours @ 80º C in air, Freeze Test: Storage @ 40º Below Zero for 100 Hours, and Altitude: 100,000 feet elevation for 100 Hours. These tests were confirmed by two independent laboratories (copies of actual test reports were available upon request.)

Late in 1976 Ragen Semiconductor, Inc. discontinued operations (due to intense competition from cheaper liquid crystal display (LCD) wristwatches) that were being produced in Asian countries. Riehl purchased all inventory and equipment associated with Synchronar production and started a new company in Whippany, NJ in 1977 that he named Riehl Time Corporation (RTC). A new direct mail order marketing strategy was launched that concentrated on technical and gadget oriented customers. The Mark III Synchronar and the Mark III Sunwatch wristwatch models were released in 1977. New features of the Mark III model allowed the user to see the frequency numbers while making accuracy adjustments.

The Sunwatch is a cost-effective version of the Synchronar. It was Riehl’s answer to the Quartz Revolution which was pricing the Synchronar (and mechanical watches) out of the market. It had a plastic (Lexan®) center bar on the top of the case [in 1980 the top design was changed to be totally flat without a bar] and an inexpensive bracelet that was priced at $129.00 vs. the Synchronar that was priced at $199.00 in 1977.

The Mark IV model was released in 1982. True to Riehl’s standards of always increasing functionality this model had more advanced features than its predecessors. An RTC press release from 1982 states that the Synchronar 2100 is “The World’s First Fully Automatic Timepiece – Programmed for perfect operation through the 21st century. Adjusts automatically for such alterations as daylight saving time and extra day of leap year.” And, is “The World’s First Perpetual Watch – It will run indefinitely on the sun’s energy…no battery replacement…ever.” The Mark IV model also included the following features: timing adjustment of up to 4 seconds per year, alarm, dual stopwatch, dual time zones and an elapsed time flasher. A later modification, in 2000, added a thin layer of stainless steel on the case back cover that did not allow the Lexan® material to be in contact with the wearer’s skin.  

On September 29, 1983 RTC filed for Chapter 11 bankruptcy. In late 1984 RTC completely ceased operations and closed their doors.

Riehl was able to acquire the assets from RTC and in 1985 Custom Circuits Corporation (CCC) was launched. CCC continued to produce Synchronar and Sunwatch model wristwatches, but in small quantities. In addition to his work at CCC Riehl worked as a technical consultant for Machine Technology Inc. in Parsippany, NJ from 1986 through 1987. One of his accomplishments while at Machine Technology was a special balancing chuck (US Patent - US4711610 A) he designed to enable proper alignment for wafer manufacturing.

Starting in the 1990s Riehl was working on a new Synchronar design, the Mark V, and was planning to complete and release it in 2006.

The Mark V was to have quite a list of advanced features including multiple time zone capability, a hundred day count down timer, a moon phase, a sidereal time function (a reference to stars), and a storage box with a built in light for solar cell re-charging. Unfortunately, Riehl passed away in 2005 and the Mark V was never released into production (although he managed to complete over 90% of the design work.)

Riehl’s youngest son, Howard, began making the Synchronar Legacy Edition in 2006 to commemorate his father’s achievements. These solar-powered wristwatches are produced using the basic design of the Mark IV model. They are limited to only a few per year. As a result, the Synchronar has been in continuous production for over 40 years which makes it one of the longest runs for any wristwatch model (especially a digital solar-powered watch.)

Synchronar Production Numbers

The exact total number of Synchronar wristwatches produced is not known. But, according to Howard Riehl approximately 60,000 total modules were made over the years.

Approx. 20,000 Synchronars (Mark I through Mark IV models).

Approx. 15,000 Sunwatches

Approx. 25,000 modules for the Synchronar and Sunwatch (many of these were used for upgrades or replacements for previously sold watches).

International Appeal for the Synchronar

Wide spread international appeal for the Synchronar ranged from the president of Egypt, Mohamed Hosni Mubarak, who was pictured wearing a Synchronar in a March 1982 article in the Nation’s Business, to Paul McCartney (of the Beatles rock group fame) who was wearing one on a June 13, 2001 CNN broadcast of the Larry King Live show.

Marketing for the Synchronar

The Synchronar Mark II information brochure asked, “Who Should Wear the Synchronar 2100?” The answer was, “This watch is the avant chic of our time. A brilliant display of technological genius. A versatile, formal, sporting, self-indulgent, solid state timepiece suited to the trendsetter”

The Synchronar Mark II information brochure also targeted women by claiming it is a fashion statement. “It is as appropriate for a woman as a man, and especially suited to the woman in business – the woman with a head for value, a feeling for fashion and a self-indulgent heart. Find the Synchronar 2100 in the finest stores. The Synchronar 2100 – The Time of Your Life”.

A 1975 television commercial for the Synchronar 2100 featured American astronaut, Gordon Cooper. His narration stated, “This is the world’s first solar powered watch. I’m Gordon Cooper, astronaut, and this is the Synchronar 2100, an advanced solid-state timepiece that is powered by Skylab-like solar cells that beam the hours, minutes and counting seconds. This Ragen micro-circuit computer is programmed to display the correct month and day for the next century. When you’ve depended on advanced technology to return safely to Earth it takes a lot to impress you. I’m impressed! See it at your jewelers. You’ll be impressed!”


Riehl not only invented the world’s first solar-powered wristwatch, but he was instrumental in many additional innovations in electronic timekeeping including: smart calendar programming, owner controlled calibration, automatic daylight savings, leap year adjustments, perpetual calendars, the first wristwatch with an accuracy to within +/- 4 seconds per year, the first wristwatch to have 3 built-in light intensities which automatically adjusted to ambient light conditions, and the first light emitting diode (LED) digital electronic wristwatch to be waterproof to a depth of 750 feet.

One can only wonder if it were not for the Quartz Revolution how popular and widespread the Synchronar would have become around the world. After all, Riehl was always challenging the status quo within the wristwatch industry. He managed to bring numerous concepts to reality through his visionary ideas, design capabilities and vigorous testing processes that were not only innovative – they were surely ahead of their time.

Popular Mechanics - December 1973 - World's First Solar-Powered Watch - p. 172, 174


The Story of Roger W. Riehl and the Synchronar

Former Egyptian President Mohamed Hosni Mubarak - wearing a Synchronar - (Nations Business - March 1982 - page 56)

The Synchronar is the first wristwatch on her left wrist - (Playboy - May 1974)

1975 Television Advertisement for the Synchronar 2100 - Narrated by American Astronaut Gordon Cooper


The World’s First Solar-Powered Wristwatch: the Synchronar

The Interesting Story of the Inventor, Roger W. Riehl, and the Obstacles he Hurdled to Design and Build this Timepiece

A lone electronics expert named Roger W. Riehl started working on the idea of a solar-powered wristwatch in the mid-1960’s. After years of testing and re-designing he released the world’s first solar-powered wristwatch in 1972. Over the next 33 years he released four models of the Synchronar (the Mark I, II, III and IV and a less expensive version called the Sunwatch.)  The Quartz Revolution, that started in the mid-1970’s, nearly wiped out the mechanical wristwatch from the world market, and the Synchronar nearly ceased production as well. Riehl managed to continue with production of the Synchronar (peak production was in 1982), but the quantities that were produced after 1982 steadily declined. Today, authentic working Synchronar wristwatches (regardless of the models or year they were made) are sought after by collectors. Read the interesting story of Roger W. Riehl’s quest to develop the Synchronar and how he was always looking to improve its functionality with leading-edge technology.

Roger W. Riehl - family portrait - circa 1973 [Courtesy of Howard Riehl]

An actual Press Release Photograph

 of 3 Synchronars - Riehl Time Corp.

A Synchronar Mark I model - some say it looks like a cobra snake head (it is surely a unique design.)