wb8foz@mthvax.cs.miami.edu (David Lesher) (03/26/91)
Donald and others {in email} have mentioned various types of tuned
ringers. I've never seen one that was tunable by a cap, but have no
reason to think that they do not exist. So I stand enlightened.
However, I want to add more noise to the circuit here :-}. Lee told me
that the usual 'across the line' ringer was NOT frequency-selective.
It cost more money to make the exotic ones that were tuned. The garden
variety ones will work on either 20 or 30 hz, and in fact a lot
farther then that. For some reason {revenge maybe - he has more, and
better, stuff in his house than the Independent does in its Strowger
office next door}. Lee was being fed 55-some hz ringing on his
single-party line. He had a hard time getting standard ringers to work
THAT far up.
Sub-Cycles do come in both 20 and 30 hz models. The 30 hz design is
much cheaper, and is what you see in old 500 series KTU power
supplies. I, however, insist on the real thing, and have 20 hz here.
[Besides, that's what I found at the hamfest for $5.00;-]
Lee never identified the the term "ferroresonant" with tuned ringers,
but I guess that is a correct description. It's worth nothing that a
few years ago North Supply listed replacement ringers for 500 sets in
four different schemes. Donald named three terms. I recall:
20, 30, 40, 50, hz [decimatic??]
22, 33, 44, 55, 66 hz
16, 25? 35.5? etc hz
But I suppose it is worth looking to see if they are still there.
He is also correct about Bell not using tuned ringers. They prefer
grounding one side of the pair, and thus adding lots of noise ;-}. I
cannot recall if the 500 set was 'gonged' or not, but guess it must
not have been. It was clearly a licensed copy, then.
As for that nine volt supply, I have NO idea what its function was. I
just recall Lee joking about adding thousands of battery snaps along
the bus bars. There was also a 'special' 48v-->48v @1000 amp machine
that was needed to provide isolated battery/ground in some CO. I also
recall a similar sized 48v-->55?v beast that provided equalization
voltage for the battery plant.
wb8foz@mthvax.cs.miami.edu (305) 255-RTFMmeier@uunet.uu.net (Rolf Meier) (04/02/91)
In article <telecom11.241.9@eecs.nwu.edu> David Lesher <wb8foz@mthvax.cs.miami.edu> writes: > few years ago North Supply listed replacement ringers for 500 sets in > four different schemes. Donald named three terms. I recall: > 20, 30, 40, 50, hz [decimatic??] > 22, 33, 44, 55, 66 hz > 16, 25? 35.5? etc hz > From REA form 522, Part III: single frequency: 20 Hz decimonic: 20 Hz 30 Hz 40 Hz 50 Hz harmonic: 16 2/3 Hz 25 Hz 33 1/3 Hz 50 Hz 66 2/3 Hz [actually I added this one since it is sometimes used] sychronomic: 20 Hz 30 Hz 42 Hz 54 Hz Another interesting spec is that the voltage increases as frequency increases, and the generator must be capable of up to 140 Vrms on the higher frequencies! Hope this helps. Rolf Meier Mitel Corporation