I have an old call box style phone that has a 425 style network in it. The call box was made by the Gamewell Company, but all of the telephone parts were sourced from telephone manufacturers.

The only markings on the network are "NET-P-75335" and the date code "9-68"

Does anyone have an idea who might be the manufacturer? Perhaps Kellogg or ITT?

I recall that 75335 is an ITT part number.

C L I C K

See pages 3 & 4.

THANK YOU!

I'll post a photo of this call box when I get a chance.

It is a pretty interesting device. The top part has a coded telegraph unit (pull for fire) and the bottom half has a telephone. There were two versions - one had the telephone for public access and the other had a locked door so that the telephone was only available for use by police and emergency personnel.

Here's some information from the patent:

https://www.freepatentsonline.com/3009023.pdf

That thing looks really neat!

It was pretty clever for the time.

Originally they needed 4 wires. One pair (usually 14 AWG) for the closed circuit telegraph loop (72 to 105 VDC) and the other pair for the telephone circuit.

Later on the design was changed to allow the telegraph and telephone circuit to use the same pair of wires.