There are 2 phones in my collection that have a so called PBX button on the shell. The Golden Glow has one on the back, the Persian Gray has it on the side. Sofar I have only seen these two positions. Which is in face a pity because I am left handed. 😉
PBX stands for Private Branch eXchange, in fact a telephone switchboard. Today these PBX’s are fully automated (PABX), but in the Ericofon times these were operated by persons or semi automated. Larger companies had a company PBX, with or without operators.
The button was used to signal the operator during a conversation. This was needed if you wanted to be connected to either an internal, external or international number, depending on the allowed actions in your case. This person would talk to you and arrange your request. These days, in an all communicating world, this can hardly be imagined anymore. The operator also handled the incoming calls, but the button does not play a role there. The picture is from Ericsson.
In automatic PBX’s one could push the PBX button during a conversation. The current conversation was put on hold and the person was given the possibility to consult a third person. Pushing the button again would resume the original conversation. If the third person would push the button then the call would be transferred and he would get the original conversation.
Looking at the inside it is just a small switch, nothing more. Here’s a picture of the inside of the Gray model. The wires are finished on the chassis and make sure the signal is being forwarded to the operator when the phone is picked up and the button is pressed. The signal is nothing more than connecting the L2-wire with an earth wire. So an extra wire is needed to use it.
There are still some questions around the PBX buttons that I am not able to answer.
In which markets were these Ericofons available? It seems that most (or all) of the models with this PBX button are from Germany. Also my 2 phones come from there. So far no other countries of origin were spotted by me and some other collectors.
Who applied the buttons? Was this done as from the Ericsson factory, or done locally by the PBX supplier under strict instructions? The latter I personally doubt.
Almost all PBX phones have the later wedge ear-piece. The flat ear-piece is hardly seen with this. And the old case I have never seen with this functionality except in case of the picture on the left which I found on the net. It could be a timing issue meaning that PBX’s became ‘popular’ in the years that the later model was introduced. The type of button on the old case slightly differs from the ones on the wedge shaped models.
If you have other information, or if you can confirm these assumptions, please let me know so we can get the story complete.
Update 12/09/15: A new phone I got is also equiped with a switch. It is a Wedgewood used in The Netherlands. See the post on ‘Disco Hospital’ from September 2015. Since I had to sand the shell I had to remove the switch.
Update 04/06/20: In a Norwegian document of the operator Televerket I came accross the term “tjenesteknapp” for this button. Meaning “servicebutton”.