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Old 16th Feb 2016, 12:26 pm   #1
EF80TVVALVE
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Default Telephone Rentals bakelite phone Conversion

Hi, I have this old 1950s bakelite phone manufactured by Telephone Rentals. It is quite a neat little phone still in original condition. Can anyone advise me on what I need to do to convert it? Ideally I'd like to keep the original line lead on it too as it is still in good condition, I do have an old GPO junction box and modern plug and wire to make this possible. I have attached some photos of the phone and it's diagram to help anyone advise me what to do.
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Old 16th Feb 2016, 1:07 pm   #2
russell_w_b
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Default Re: Telephone Rentals bakelite phone Conversion

I did one of these up: nice instruments. It isn't as simple to convert them, as they're 'cut down' versions of the 300 series instrument with fewer accessible terminals.

I cut the wire to the capacitor and took the blue wire of my standard BT plug and lead directly to the bell, as per the modified (attached) diagram. White to pin 2 of your standard BT plug, red to pin 5 , and blue to pin 4. If you feel the need to fit a 3K resistor to reduce the REN, then replace the link between the bell bobbins with one, or connect between terms. 1 and 2 in lieu of the white link at 'X'. It's a soldering-iron job!
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Old 23rd Feb 2016, 8:51 am   #3
Relay Automatic
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Default Re: Telephone Rentals bakelite phone Conversion

The phone is actually made by British Ericsson as a Model 1000. Ericsson supplied a range phones to TR See Rob's British Telephone web site for details.
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Old 23rd Feb 2016, 1:34 pm   #4
vosperd
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Default Re: Telephone Rentals bakelite phone Conversion

Referred to as the "K89" by TR engineers due to its TR part nunber.
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Old 23rd Feb 2016, 4:53 pm   #5
TonyDuell
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Default Re: Telephone Rentals bakelite phone Conversion

If you have a separate ADSL filter for each telephone (implying a separate ring capacitor for each socket) and/or don't care about bell tinkle (I am not sure why this is ever a real problem) then you can avoid much of the conversion by wiring the telephone as the manuacturer intended and simply connecting the A and B line wires to the line (outside 2 contacts -- 2 and 5 -- of a BT Plug 431A).

The bell is of course a 1k one, and it is a good idea to put a 3k3 resistor in series with it. The obvious place to do that is in place of the EB (Extension Bell) strap.
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