Dual Dial test telephone

[dsk]

I have a test telephone made at Oslo Telefon Anlegg (Oslo telephone company) It has a low speed dial 9.16 pps, and a high speed dial at 13.53 pps (measured today after decades in storage)

It has one button adding a 100 ohms resistor in series whith the phone, one adding 700 ohms, a button for ringer no 2 (1000 ohms + 2 microfarad) x1 and x2 one for adding 20 k across the line, and one for grounding the b wire.

I measured the ringer load as described in Ralph O. Meyer's book: "Old-Time Telephones!" and the load is approx 4.25 and 8.5 times the load of my Western Electric 500.  at 25 Hz.  Or an impedance of 2290 and 1145 ohms!  (This will be only rough numbers)

The induction coil has 4 terminals marked 1 2  17 ohm and 4 3  26 ohms. 

My guess will be that this one is made about end of WWii of available parts, cords and one dial is changed later. The oldest parts are probably the hooksw and induction coil from before 1930 when anti sidetone was made standard here.


dsk

[dsk]

More pictures

[paul-f]

Very nice!

It definitely would stand out in a collection display.