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Trimphones: 712 (Prototype) & 722

Started by GeneGenie, September 25, 2013, 08:37:25 AM

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GeneGenie

Hello, I'm new to the forum as well as the phone collecting thing. Not sure if my recent find is as 'outstanding' as I'd like to think but it's certainly rare so I thought I share it on here. What I got is a 712 Field trial Trimphone - two of them to be precise (I think there were only 10 000 copies made, no idea how many have made it to present day). Got them on eBay for £60 including postage. They aren't in excellent condition, in fact they're fairly knackered (cracked handset, stiff dial, that sort of thing). Neither of them have a correct plug so can't say whether either of them works. However, if I put some work in then maybe I can get at least one of them up and running.

AE_Collector

Hi GeneGenie:  Welcome to the Classic Rotary Phone Forum.

I don't know much about Trimphones. What features do these have that shows tha tthey are fieldtrials, or is it something in the numbering? Neat looking phones. You should be able to get them looking real good without too much effort.

Terry

GeneGenie

Basically, 712 Trimphones were the first Trimphone prototypes, they look slightly different to 722 - the final improved version of Trimphones which were later mass produced. Apart from different electronic bits inside (the original Trimphones had 706 circuitry stuffed into a smaller case) the main difference in the design is that there are letters on the dial which 722 don't have, also the screw holding the handset together is placed at the top rather than the side. Those are the main features that distinguish the two models although I'm sure there's more if you look close enough.

HarrySmith

Welcome ;D
I was going to post my usual warning about Phoneitis but after reading your last post I think it is too late:(
How many phones do you have?
Can you post a picture of the 2 different models side by side?
Harry Smith
ATCA 4434
TCI

"There is no try,
there is only
do or do not"

GeneGenie

Hi HarrySmith, I currently own 15 phones, 5 of which are Trimphones, but my collection is still expanding, I intend to get many more in the future, it's just the case of finding the right one at the right time for the right price, I'm sure you know the drill..
Right, here are the photos; I compared my beige 712 with a (what used to be) beige 722. Hope they have enough detail but let me know if you want more. Sorry for the dodgy picture quality, I haven't got a proper camera.

GeneGenie

And should someone be interested in the insides, I took some pictures of that too. :) Sorry for clogging up the Find Of The Month thread, I'm sure this belongs somewhere with the Trimphones section.

gpo706

Your 2 have "party line" buttons fitted, easy to disconnect and rewire.
"now this should take five minutes, where's me screwdriver went now..?"

AE_Collector

What would "Party Line Buttons" do?

Terry

Owain

Quote from: AE_Collector on September 26, 2013, 03:44:53 PM
What would "Party Line Buttons" do?

Where two subscribers share the same copper pair, the button sends a fleeting earth-to-A-wire to indicate to a relay set at the exchange which subscriber is calling so the call can be metered appropriately (no free local calls in the UK until the 1990s)

GPO phones were sent out with the button wired A-to-Earth, at the X subscriber it was connected to A and B (tip and ring), at the Y subscriber the A and B wires were reversed where the line came into the house to the Y subscriber had B-to-earth.

Party line with separate metering started in 1924 and lasted well into the 1980s especially in rural areas.


HarrySmith

Thanks for the photos, side by side shows the differences quite well.
Looks like I was right, you are fully in the grips of Phonitis ;D
Harry Smith
ATCA 4434
TCI

"There is no try,
there is only
do or do not"

AE_Collector

So the Party Line button had to be pushed for every call made to ID the caller? What would happen if not pushed? Was there dial tone even if not pushed?

For long Distance here we had ONI (Operator Number Identification) on many types of exchange equipment whe nmaking Long Distance Calls. Once this was automated in many instances it was still ONI on party lines. Operator would come on the line after you dialed the LD call and say "Number please" which was a request for your number for the billing. Then the cal lwent through.

I recall adding ANI equipment to our SxS offices in the late 70's and early 80's to automate the LD billing on private and 2 party lines. 4 party where they still existed remained ONI. Ironic that our ANI equipment was made by ATI in GB while you were pushing party line buttons to ID the caller!

Terry

Owain

Quote from: AE_Collector on September 26, 2013, 05:44:42 PM
So the Party Line button had to be pushed for every call made to ID the caller? What would happen if not pushed? Was there dial tone even if not pushed?

Yes.

Nothing (unless the other party was using the line in which case you would overhear them). This was a 'feature' so you could interrupt them if you needed to make an emergency hall.

No. The button had to be pressed so the relay set connected the copper pair to the appropriate linefinder for your line. Only the copper pair was shared, each line had its own linefinder, meter etc.