My first job, after college, was with Western Union Telegraph Company in Philadelphia where I was the engineer assigned to the Telex Exchange.

I knew little about Central Office technology. All I had was an interest in Teletype machines and RTTY. But, there I was, responsible for an ITT CSR-4 Telex Exchange. The CSR stood for Circuit Switch Reed as the exchange, manufactured at ITT Milan, TN, used reed relays for the directional matrix. Imagine an entire floor of an office building filled by a Telex Exchange Central Office. Over 1200 direct subscribers using both polar and loop switching plus over 600 trunk circuits! The clatter was similar to a number 5 crossbar machine but more compact. The Western Union Technical Review has an article about the CSR-4 in July 1966.

Russ WA3FRP

i-Telex 834328 WUTMPAM CHIL

Sent from my iPhone

On Feb 15, 2025, at 9:59 PM, Brenda Gentry via GreenKeys <[email protected]> wrote:

Are there any greenkeyers who also take interest in telephone central office switching?

B. Gentry KA2IVY

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