The sinking of the Titanic resulted in the Radio Act of 1912 that required 24-hour radio watches. The disaster also led to clocks in the newer radio rooms featuring three-minute periods marked in red. That three minutes provided a silent period when only emergency radio messages could be transmitted.

I've always been fascinated by these clocks used in shipboard radio shacks. See the below diagram from the Chelsea Clock Company (USA) Special Radio Room Clock.


In the US Government specifications for the Chelsea clock, it notes "the dial has accurate 4 second marks in red around the outside edge, over which the sweep seconds hand passes, enabling the radio operator to accurately transmit the 4 second alarm signal provided by the International Telecommunication Convention and the International Conference on Safety of Life at Sea." And later, it indicates that, "also marked in red on the dial, clearly and forcibly calling attention to the radio operator thereto, are the two 3 minute silent periods which must be observed by all radio stations at 15 and 45 minutes past each hour." Thus, the red marks on the dial edge are for the seconds alarm, and the red sector triangles for 3 minute radio silent periods on the 500 kcs. distress frequency. Later models featured additional green sectors at the top of each hour and 30 minutes past each hour for the monitoring of the 2182 kcs. distress frequency.




The original Chelsea model is still made by the manufacturer and retails for quite a lot of money. Antique Chelseas are going for big bucks too. So I adapted the design and made my own inexpensive versions, manufactured by CafePress.

Click on the pic to find out how you can get one. 


REVIEWS from buyers...

For under 15 bucks it's great. I've had clocks costing twice as much with quality not half as good.  - W3DCG

Good value, looks good, keeps good time. Makes the ham shack into a real radio room.  - W4PC

Bought two after reading other reviews. Keeps excellent time, price is a bargain and looks great.  - KL7RHJ

Absolutely GREAT!!!  I have purchased 5 of these. I bought one to see what the quality was, and after receiving it, I purchased 4 more. - N6VQQ

Ordered one of each for K6AA at the Los Angeles Maritime Museum. Great conversation pieces at shoestring prices. - W6HB

I cannot recommend these clocks high enough. They are an excellent time keeper and the price is right!! - W4WQ