What's this in a 302 F1 handset?

[TelePlay]

There appears to be a condenser in the transmitter of the F1 handset that came with a 1948 302.

It's stamped 129 F COND and dated IV 49.

It connects between the black and red wires inside the transmitter side of the handset.

What is this? Why is it in there or what was it used for? Is it still needed?

[Phonesrfun]

Early F1 handsets and most E1 handsets had this condenser (capacitor).  Its purpose was to keep electrical discharges from effecting the carbon granuals in the transmitter element.

Improvements in carbon composition in the transmitter design caused the Bell System to omit it entirely in later designs.

The transmitter is in series with the primary winding of the induction coil when it is connected to the phone line.  When the phone is hung up, the hookswitch opens the circuit, causing the electromagnetic field in the inductor to collapse.  When this happens, there is an electrical discharge of only a few microseconds that discharges back through the transmitter.  This had the effect of arcing through the carbon granuals in the transmitter, causing them to wear out, so to speak.

By the time the 302's were being built, the capacitor was not used.  Perhaps the handset is a transplant from an earlier phone, or it was just simply an early one on the 302.  I would say that if the transmitter element is dated after about 1940, the capacitor can certainly be safely taken out, as they are a bear to work around in such a tight space.

[poplar1]

These condensers are found in the  handsets marked "F1W," which were sold to the Independent phone companies. They are usually not in the handsets marked "F1" sold to the Bell System."

Is your handset marked F1W or F1 on the handle?

David Willingham

Connections for the 8-conductor plug (upper housing):

Green--->BB on terminal plate<-----(blue)BB on dial
Yellow--> Y on terminal plate<-------(yellow)Y on dial
Black--->R on terminal plate<--------(black)BK on dial
Red----->B on network
White--->R on network
Blue----->C on network
Orange-->A on network
Violet---->K on network
               GN on network<----------(white)W on dial

Connector on Backplate:

Green--->BBX of switch hook
Yellow--->SL of switch hook
Black
Red------>T of yellow terminal block
White---->TR of yellow terminal block
Blue------>R of switch hook
Orange--->R of switch hook
Yellow---->? (terminal with red ringer wire)

[TelePlay]

Is your handset marked F1W or F1 on the handle?

Thanks for the history and electronics lesson on the condenser/capacitor. Never saw one before but that makes sense.

And, yes, the handset is an F1W with 2-50 elements, an F1 transmitter and an H1 receiver. In checking, discovered the last person to open the receiver cross threaded the cap and it took a liberal amount of WD-40, a hair dryer and my large strap wrench to get it off. No damage. Screws back on and off and on very well now.

And, the original handset cord is a 5 foot long coiled cord which I thought was added after the fact but it seems original to the F1W.

This also answers my question about the date stamps in the base. Both the base and the ringer are dated 9-48-A, the 4-48 dial (with a Z/Operator/O plate) is marked 5H*, the base is marked H1 in vermilion but is date stamped 6-23-48-2 in yellow/green.

So, that would seem the phone was made by WE for another company. I bought it as a gift for my brother-in-law and that's where it will go.

Since the number plate has the Z/Operator/0 but with worn lettering, don't know if I will switch it out with a 5H dial with an 0/Operator plate that I have or leave it with the phone.

Anyway, thanks for the help on the condenser/capacitor and F1W lead. That answered a lot of question I had on this phone.