Communications – telephone notes on getting them to work after a pole shift.

Subject Telephone
sent 24 DEC 98

Its a true statement the phone systems will be permanently dead. But this does 
not necessary mean you can not use some of the older equipment to do point to 
point communications with point to point wiring.  You will not be hearing a dial 
tone. You can add make shift buzzer or bell. However, communications over wire 
can be established for a short predetermined hard wired point to point sites.  
This could be between close neighbor, or members of a small community.  The 
following is the current alternatives. 

After may weeks of off line back and forth communications with the help of a 
friend who wishes to stay anonymous. Involved much bench testing by both of us.  
The following is the bottom line.  Only had success with the old phones that 
have the Bridge network box in them. This is the old 500 series made by Bell 
Western Electric and General telephone and possibly others. Open them up and 
check to see they look like figure 1 inside.  If you find any of these units at 
a garage sales or after the PS the best is to use them as they are. As of now 
nothing else will work of the existing telephone equipment. 

The easiest way to get into operation is to use the model 500 series telephone 
set as it exists. Apply a 3v to 9volt battery. 6 Volts would be optimum.  If you 
use higher voltage then check out figure 6.


Figure 2 is the most basic way to get old phone equipment back into some use for 
local primitive communications.  The handset or operators headset can be used 
directly with a battery voltage between 3 volts and 9 volts.  However, the 
optimum is about 7 Volts.  The handset is what you put up near your ear and 
mouth and is from the old rotary dial or keypad dial type telephone set as 
identified by having the network bridge box as in figure 1.  Three wires need to 
be run between each hand or headset.  Note that the battery is in use and 
draining current all the time while is it hooked up.  The unit has no ring or 
buzzer capability.  However, it may find some short time use.  It works best for 
two or more that need to do near constant communication from a relatively short 
non-moving location. 

Figure 3 can be used if one has more than two phone that need to be hooked 
together. 

Figure 4 adds a momentary contact switch so as to save battery power.  Each 
person would push the talk button to allow battery power to power the operation 
for all who are on the line.  One would need to scrounge the momentary push 
buttons from other electronics equipment.  The telephone set it's self has a 
multi-contact momentary contact switch that could be used.  One could also make 
one from a bent paper clip screwed to a wood block. One pushes down on the paper 
clip and it touches the head of a screw.  There is also momentary contact 
switches in the phone the headset was taken from. The receiver switch would 
work. 

Figure 5 adds a buzzer or bell to each site.  Each person can ring or buzz all 
other hand or headsets.  The buzzers or bells could be scrounged from car parts 
or door bells/buzzers (some of these will work on DC). 

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Notes on bench testing

Did get it to work. Grounding was not the issue. Once it was working I could 
ground any part of it and it didn't improve sound volume at the receiver of the 
opposite headset. 

I was using a 12V Gel cell battery, and thus needed to use a variable resistor 
to bring the voltage down to about 6 Volts for operation.  This resistor was 
reducing the sound in the receiver.  Also the carbon transmitter tends to fall 
into a semi-dead state where it is insensitive to sound.  This is accompanied by 
a increased current flow and sense this was being limited by a pot set to 313 
ohms then the voltage dropped across the headset went to about 1.5 volt in a no 
sound condition.  Thus it goes into a sort of dormant attenuated talk mode.  The 
current flow goes from 19 ma in operation to 33 ma in sleep mode.  .019*12 = 
.228 watt to .033*12 = .396 watt.  It takes taping on the transmitter or talking 
to wake it up.  To make this circuit ultimately work I needed to add 2 uf 
capacitor across R to T lines.  See figure tel5 for battery setup that worked.  
This accidental discovery could have benefits of saving some power for those who 
do not add a talk switch.  

I found using a 6V gel cell without any capacitor works. The only problem is 
when not in use the current goes up to 125 ma.  Power consumption 6v*.127ma = 
.76 watt in sleep not sound mode.  This is for the older handset and the newer 
one unplugged.  Minimum power in use is about 19ma*6v = .11 watt.  



Questions:
all of the above work was hampered by not having 2 of the same kind of handset.  
One old and one newer one.  Thus not totally operational got only one way flow 
from old transmitter to newer receiver.  I need you to verify voltages and 
currents and power of the above before I publish numbers. 

Why is it that some more modern phones that runs on telephone company 48v DC 
will not work for us?  I have observer it but don't know why.  Is there some 
handshaking that goes on when the dial tone is sent? I measure my phone line 
coming in and I have one ground wire and -51 Volts. If I supply that to any 
current phone that runs totally off this voltage why can  not one get these 
newer telephone sets to send and receive? It has been my experience so far that 
it doesn't work.  The voltage drops down to about 6 volts during operation so is 
a resistance needed to simulate long phone lines?  I even tried this to no 
result. 

The flex cable attached to the handset was designed to be flexible and not break 
over a long time.  Because of this it was designed with thin foil wrapped around 
a strong nonconductive core.  Soldering to this can become a challenge.  I plan 
to recommend remove as much as you can of the fiber core. Carefully unwrap the 
foil and attach your wire to this.  Support the connection with much tape so 
that it will not flex or stretch.  Do you have a better recommendation? 

I did find floating DC to work in all cases with handsets. Is this a problem 
with Telephone sets?

I think as far as the ringer is concerned. we just recommend using a separate 
bell or buzzer circuit is best.  I don't think it's worth you time to design a 
90 volt 20 cycle circuit.  And I don't think I want to recommend using rectified 
110V with a togo switch.  The power supply I used was design to kick of it too 
low a resistance was encountered. It also had a small light bulb as a limiting 
resistor. I think this would be to complex for most and the likely hood of 
burning out there phone equipment to high. Thus your first recommendation is 
best go with a separate buzzer or bell. 

I think I have observed a slight bit more sound out of Tel4 then Tel1 modified 
with using Tel5 battery circuit to allow it to work.  Can you confirm or 
disagree with this observation?

If one uses 48 Volts with the telephone set as you diagramed in fig1.  Does one 
need a limiting resistor so the voltage drops to about 7 volts when it is in 
operation? 

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I did the graphics for tel1, tel2, tel3 and then wrote the above and then did 
the following testing.

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Bench testing results: (testing whole telephone set with out taking it apart_

Types of phones tested: Continental telephone system ITT, Bell system Western 
Electric, General telephone, pacific telephone, Radio shack phones, Conairphone.

Did some bell testing to see if I could get the bell to ring on some of the old 
phones I have.  Used 115V AC rectified with full wave bridge to DC became about 
170 Volt with a 40 uf capacitor to filter it. With a DPDT switch I was able to 
reverse the polarity and get the bell on some phones to ring once each flick of 
the switch.  This is with no modification of the phone and the receiver on the 
hook.  I sent this switched DC into each phone then tested ringing several 
phones at a time.  it work as long as one reverses polarity with the DPDT 
switch.  Found I could put between 6K to 36K ohms and still get it to ring.  
This gave me an idea to test using 2.5k to 4K ohms or a resulting voltage on the 
phone of 5 to 3.7 volts once both phones were off the hook.  Well this is where 
I ran into problems.  None of my phones would work with this rectified DC or nor 
when I used a 12 V Sealed Lead Acid battery nor when I boosted it to 48 V DC.  I 
tried parallel and series connected battery. I turned the place upside down, 
couldn't find any of my old bell 500 model units.  But the whole thing got me to 
thinking.  There is something fundamental that I don't understand about modern 
phones.   These things must work off DC why can I not supply the DC and get them 
to work.  I am now thinking that the DC source needs to have some internal high 
impedance otherwise all the sound will be shorted into the battery.  I was using 
a resistance between the high voltage DC and the phones and it didn't work. What 
am I missing?  What don't I understand about more modern phones than the bell 
500 model.   Note.  I was attempting to doing what most will do when they find 
they don't have a old bell 500 phone.  That is make do with what you have.  

Notes on what phones have bells that work: I got the bell to sound on several 
Small conairphone (keypad on headset) also on a trimline western electric and on 
a continental telephone set.  I found to look for slide bar or know to change 
volume on bottom to see if it has a bell.  If it has slots or holes around in a 
circle then it most probably has a electronic speaker and will not work.  I did 
find one slimline phone that had holes in a rectangular shape and had a bell.  
Radio shack telephone set with Keypad model 43-365 with speaker in bottom that 
does not work.

Note: None of these telephone sets worked when hook together with a battery in 
parallel or series. 

Now bench testing using handsets only:

Is there a standard for position of the wire in the modular plug?  I find wwrb 
(white, white, red, black ITT) or wwwr (radio shack) bwwr (slimline phones).   
Using my tone generator It test out sometimes the receiver was wired to the two 
in the center and sometimes to number 2 and 4. Green and red transmitter and 
yellow and black as receiver.  Conclusion no standard.  Will need to do 
continuity checking and visual break apart color checking. 

Tried using a Octopus multi-connector to bring many lines together for the 
smaller modular connection.  didn't work doesn't fit correctly.  Finely took the 
phone apart and took the wires off the phone and plugged the handset into this 
modular jack.  Then wired two handsets up for a test. 

Your fig3 and my tel1 did not work no sound. All the sound is going into the 
battery, never makes it over to the other handset.   Your fig2 does work to the 
degree I could test it, however I found tel4 also works.  At this rate we will 
only be able to get 2 phones working at one time, no three way conversions. Do 
you see it the same way?  Hope you have a way around this.

My testing is incomplete. I was using one modern handset off a radio shack 
telephone set and one real old handset without the modular plugs.  I don't at 
this time have two of the old handsets.  But I can tell you what I found with 
this situation. 

Optimum sound transmission was estimated to be at about 7 volt .125 amp battery 
draw.  The only thing that worked was the transmitter on the old phone and 
receiver on newer headset. The reverse does not work.  It does have 1.5 volts on 
transmitter the new phone and the receiver (speaker) of old phone has .76V. 
Sputter testing by jiggling battery confections works I can hear both receivers 
work.  I expect the impedance of the new phone transmitter doesn't match the old 
phone receiver. Had one other newer type handset. Gave the same result would not 
transmit.

I am assuming if one had 2 of the old type phone headset both transmit and 
receive would work on both. However, until one of us can fully test this I can 
not publish it as a recommendation. 

Summary - Not able to get more modern equipment than possible the old 500 bell 
western electric type phone to properly work. Whether using handset only or the 
full phone. Able to get bell to ring if one wants to drive the unit with high 
voltage DC and use a toggle switch. 

What can you add to all this?  Any comments or suggestions?


