[GreenKeys] Telephone Hand Crank Dynamo

[Frank]

On Tue, 16 Jun 2015 21:54:18 -0500
Cory Heisterkamp <coryheisterkamp at gmail.com> wrote:

> Roy, that's pretty much it. Even into the 40's (and some places,
> later), some rural independents offered desksets that operated off
> the central office 'battery' for voice but still contained a small
> magneto to 'ring in'. 'Leich' seems to be the most prevalent and you
> can set up a nice intercom system with a pair of these. 
> 
> I've got a Western Electric 555 Switchboard in the other building
> (these were used for PBX service rather than at a central exchange).
> An optional feature this one has is a built-in magneto to allow the
> operator to generate the ringing current in the event that AC was
> lost. Otherwise you just press a button on the cordset pair and it
> takes care of itself. The associated lights will tell you when the
> party answers and when the call is complete. -C
> 
> 
> 
> On Jun 16, 2015, at 9:37 PM, drlegendre . wrote:
> 
> > As I have come to understand it..
> > 
> > In the very early days, the hand-crank magneto served only one
> > purpose - to ring a bell down at 'central' (the phone company
> > office) - it did not supply current for the voice circuit - that
> > was done by the talk battery. In those days, a local system might
> > have only a couple dozen circuits, at the most. 
> > 
> > When the operator heard you ring-in, they would connect your line
> > to a talk battery, with their headset (or handset) on the other end
> > of the loop. You'd then tell the operator who you wished to call,
> > and the operator would then connect the recipient's line to the
> > operator's crank magneto - and then the operator would use their
> > mag to ring the bell on the recipient's phone. In some cases, the
> > operator would connect the two lines at that time, and allow you to
> > use your mag to ring the recipient's bell, if the distance was
> > short enough. 
> > 
> > Once the recipient answered, the operator would say "call from Ray
> > Morgan" (if needed) and connect the two lines together on a talk
> > battery loop. The operator would then listen-in only as needed
> > (...) and when the conversation was over, they'd re-connect all of
> > the circuits back to the default jacks. 
> > 
> > Please feel free to correct this..
> > 
> > On Tue, Jun 16, 2015 at 7:32 PM, Roy Morgan <k1lky68 at gmail.com>
> > wrote:
> > 
> > On Jun 15, 2015, at 12:01 PM, Howard Weeks <weeksh at att.net> wrote:
> > 
> > > Roy,
> > >
> > > Those things will produce up to about 80 - 100 volts depending on
> > > the crank speed and condition of contacts, On 6/15/2015 11:32 AM,
> > > Roy Morgan wrote:
> > >> Greenkeyers and telephone historians,
> > >>
> > >> I have acquired a hand crank dynamo of the sort used in ole time
> > >> telephones.
> > 
> > Thanks to all for information about the hand crank telephone
> > dynamotor:
> > - 80 to 100 volts
> > - about 20 cycles
> > - rings a bell or other device at the operators place
> > - will bite you if you are careless
> > - wil bring worms up from the ground
> > 
> > It’s nice to hear from folks who remember using them (even while
> > standing on a chair to reach the thing!)
> > 
>


	To sort of clarify things a little - "local battery" lines were
	"dry" no DC current.   A source of DC at each telephone,
	usually two No. 6 dry cells powered the transmitter at each
	phone.   None of this current passed on to the line.  The same
	was true of the switchboard (if any) connected to the line.
	The only way to signal - either to alert a switchboard Opr. or
	to call another phone on the line was by means of the AC
	voltage generated by the hand cranked generator (or, later by a
	"sub-cycle" freq. converter)  
	"Common battery" circuits - which are the kind everyone
	is now familiar with - have DC at +/- 48 V on the
	line.  When no phone on the line is "off-hook", no
	appreciable current flows.   When any phone goes off
	hook, the current flow is detected by the CO (Central
	Office) equipment and the Operator is signaled (manual
	system) or dial tone is returned (automatic).  Ringing is still
	done by 20 Hz AC, but none of it is generated by hand
	cranking.    Multiple party lines used different schemes of
	ringing for up to 4 parties individually.  I had a 2 party
	line at my house in Chicago until about 1950
	All of which has little to do with Greenkeys, but since
	somebody brought it up...