Author Topic: Western Electric 306, 5306, and 356 telephones circuit and wiring  (Read 1510 times)

unbeldi

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The Western Electric 306 telephone is similar to the 302 type telephone, with the exception of the ringing circuit which consists of a B3A low-impedance ringer combined with a 333A, 372A, or 426A gas-filled electron tube, instead of a ringing condenser.

The 306 telephone housing was coded H5. It has a No. 101A induction coil and a 195C condenser, which contains only a single 2 F capacitor for the audio circuit.

The phenol plastic terminal mounting plate has terminal screws labeled GND, K, and E.

The set may be equipped with a No. 61P radio frequency filter.

The wall-mounted version of the 306 is the Type 356 telephone with an M5 handset mounting.

In 1955, until the mid-1960s, WECo provided new housings, similar to the 500-type set, to replace the 302-type housings to produce modern-looking telephone sets, now designated as the 5306.

The 306, 5306, and the 356 type telephones were used for 4-party full-selective and 8-party semi-selective service.   Four-party selective service was achieved due to the polarity-sensitive operation of the electron tube diode in conjunction with divided ringing for two tip-party stations and two ring-party stations on the line.  The A.C. ringing voltage was superimposed on the D.C. battery level at the central office. Two stations received ringing voltage via the ring side of the line and ground, and two more stations were rung from the tip side.  For each of the two stations on one side of the line, the D.C. polarity was reversed, so that the electron tube would only fire for one station, and thus only activate one ringer. 

To achieve this, the ringing bridge of each station on the line was wired slightly differently.  This polarity scheme is depicted in the first attached image.

For eight-party line service, four sets of two identically wired telephones were connected to the line.  The two identical stations were notified of incoming calls by code ringing.

The second image shows the electric circuit principle of the telephone.  The circuit is drawn with the telephone in the on-hook state.  The wiring is for ring-side station receiving negative polarity superimposed power ringing, i.e. the "A" station in the line schematic.

The last schematic is the wiring diagram of the 306 set, from Catalog 11 (1950), but with color-annotated wires.


Other articles:
- TBD
I am replacing my local images of this circuit in other articles with links here.


Diagrams
  • Circuit diagram drawn acc. to Catalog No. 11 (1950)
  • Dial set (306B, 306C) factory wiring diagram of Catalog No. 11, annotated in color
  • Manual set (306A) factory wiring diagram of Catalog No. 11
« Last Edit: June 17, 2017, 02:10:02 PM by unbeldi »