Western Electric H7

[Doug Rose]

last week Janet found a large stash of phones, mostly 302s. I started to refurb one today and found it to be an H7. Not quite sure what it was used for but lo and behold it works perfectly. Everything is gated 3/50. except the dial which is a 51. I was happy when i plugged it in and it worked, but amazed when it rang. It is really in like new condition. Any insight into the H7. ....Doug

[Nilsog]

I think I also have an H7, but it looks different than yours. I'll have to dig it out and compare them.

EDIT: Check that, I don't have an H7... I do have an AB1 though. Anyway, here's what  paul-f's site says about the H7:

http://paul-f.com/we307.html

[Babybearjs]

thats a WE 307C. I have a bunch of these and have been very successful in converting them back to CB service. they were originally for rural service and were wired for LB service. they seem to be quite rare and are worth $249.99 if sold in restored condition (working) I love mine and love the fact that they are so versatile in the wiring.

[Doug Rose]

thats a WE 307C. I have a bunch of these and have been very successful in converting them back to CB service. they were originally for rural service and were wired for LB service. they seem to be quite rare and are worth $249.99 if sold in restored condition (working) I love mine and love the fact that they are so versatile in the wiring.

thanks for the info John. It will be on eBay Sunday at a much cheaper price....thanks...Doug

[Nilsog]

I knew I wasn't crazy... I just found my H7.

[wfs1933]

I just got a 1949 H7 (with a dial blank) and wonder what this  266A inductor is?  its mounted by the ringer and why is the condencer diff then a reg 302?  Thanks

[dsk]

Never heard about H7 except as the initials as our king about WWII

Please enlighten me.

dsk

[unbeldi]

I just got a 1949 H7 (with a dial blank) and wonder what this  266A inductor is?  its mounted by the ringer and why is the condencer diff then a reg 302?  Thanks

The WECo 307-type telephone set was used for local-battery talking common-battery signaling stations (LBT-CBS) with anti-sidetone compensation on very long local loops. Beyond a certain distance the local loop may have provided too little current to operate the transmitter and/or the receiver reliably, but still enough for dial operation in automatic service.  Anti-sidetone balancing was also effected when the set operated inefficiently in low current.

Thus, the telephone required a battery to be connected to run the transmitter. Powered by a battery, the transmitter could not be connected directly into the central office loop as in most common-battery talking circuits, but had to be separated. Instead, the receiver is taking the place in the loop. However, since the receiver must not be traversed by DC current to prevent the magnet from demagnetizing over the long run, but also to operate it in its proper electro-mechanical conditions to reproduce speech faithfully as designed, it is protected by a capacitor (2 µF) connected in series with the receiver. A capacitor blocks direct current.

This capacitor presents a dilemma for the circuit's function in line supervision, i.e. signaling, because when the telephone does not  maintain a flow of DC through the loop circuit, the central office equipment assumes that the user has hung up the telephone. The telephone must provide a DC current flow while the telephone is off-hook. When the set goes off-hook the exchange recognizes that as a signal to provide a digit register and dial tone, and when it stops, the phone call has ended.

This is the function of the 266A inductor. It is a copper wire coil with 90 Ω DC resistance wound around a silicon-steel core.
As an inductor it provides a high impedance to speech current (AC), while having a relatively low resistance for direct current.  It is connected across the receiver and capacitor to provide the mentioned DC path for signaling. It permits the DC current to pass, but it prevent the AC speech from shorting by blocking it; it allows speech to flow through the receiver instead.

The capacitor in a 307 is also new. It has not two, as is typical for the standard 300-type set, but three condensers packed into the same housing. The additional capacitor (0.5 µF) is used in the anti-sidetone balancing network, which in this set consists of a 300 Ω resistance and this capacitor in series with the tertiary balancing coil of the 104A. The third capacitor (0.5 µF), of course, is in the ringing circuit as usual.

The 307 uses the 104A induction coil, which is for anti-sidetone local-battery service. It has an especially low primary winding of only 2.3 Ω resistance for the transmitter circuit, to reduce DC loss as much as possible to increase transmitter efficiency.

There were two principal versions of the 307.  One had an F1 handset (307A/B/C/D) and one with an F2 handset (307E/G/F/H). The first letter in each set is the type for manual service (307A and 307E), as you have here.  The F1 handset had a 3-conductor cord, as was typical for all 300-series telephones. The transmitter and receiver circuits were connected to save the material of one conductor in the handset cord. The F2 handset, however, had four conductors, because it separated the transmitter and receiver circuits completely. The benefit of this arrangement was that when the customer had several 307 telephones in close proximity, they could all be operated from the same battery with a 634BD set for each.

The housing of 307 telephones is marked H7. It has an additional hookswitch contact over the 302 type (H1), similar to the 304 (H3), but using different color coding of the leads.

[dsk]

Thank you! That explanation is really good. 
dsk

[Babybearjs]

I have several of these... once converted, they work great!

[unbeldi]

I have several of these... once converted, they work great!

They work great just the way they were intended, designed, and made. And that is the only way they operate correctly.

Many things, telephones, and others can be made to work in various ways, but these cannot be operated with the same efficiency in another way. All components are tuned to each other for the intended purpose.
If you want to operate a 302, then buy a 302, it doesn't look or feel any different. They are plentiful and cheap.

Owning or operating a 307 has no other purpose today than demonstrating a piece of history. As such it makes no sense to operate it any other way.

[Babybearjs]

The reason I mentioned this was because of the jumper on the "C" terminal, please explain the purpose of this item? what was the jumper meant to do??

[unbeldi]

The reason I mentioned this was because of the jumper on the "C" terminal, please explain the purpose of this item? what was the jumper meant to do??

The jumper wire was used to provide some tuning so that the anti-sidetone network impedance could be adjusted to the actual loop length to the central office. The wire would be used to short across the 300 Ω resistor. That's why it is normally connected with both spade lugs to the C terminal.

This is also the reason that the 104A induction coils uses an additional resistor in a distinct component, rather than being integrated into the tertiary winding by using a higher resistance coil wire, as was practiced in the 101A induction coil of the 302. There it saved material and manufacturing cost by having one component provide both the anti-sidetone cancellation AND the balancing network in one piece part.  The coil in the 104A still has this feature, it also has a high impedance (200 Ω DC resistance), but this was not sufficient for very long loops.  They deemed it necessary to adjust the balancing network in the field according to the local condition found at the station. So they provided the possibility for adjustment by having a distinct resistance and the bridging wire.

Some other independents' manufacturers of anti-sidetone telephone sets provided potentiometers in their set to adjust properly for resistance to the central office.

[Babybearjs]

Explain "Tuning" what would they have done to the phone to tune it... where would they have put the jumper?

[unbeldi]

Explain "Tuning" what would they have done to the phone to tune it... where would they have put the jumper?

Across the resistor, from C to A, for example.
Or to R removing both, the resistor and the capacitor.