The coils of Trembler Bells should to connected in series when the operating current is obtained from the Exchange Line, and in parallel when the operating current is obtained from local primary cells.  The relevant Extension Plan. No. Diagram Notes will state how the bell coil should be connected.

2. BELLS No.56 and 65A

  1. Loosen the gong and twist it clear of the striker when the armature is hand operated.
  2. Loosen the locking screw; and withdraw the contact screw until its tip is clear of the contact spring.
  3. Check that the contact and tension springs are approximately parallel to the armature.
  4. Adjust the contact screw so that its tip just touches the contact spring when the armature is hand operated.  Then withdraw the screw three half turns.
  5. Tighten the tension adjusting screw until the contact screw is just made.  Tighten the locking nut, holding the tension adjusting screw firm with Screwdriver Inst. No. 1. or spikes Capstan No. 3C.
  6. Adjust the Gong until the striker just touches it with the armature hand operated.  Then tighten the looking nuts.
  7. The bell now gives the lowest volume of sound which can be obtained reliably.  To increase the volume, screw in the contact screw until the required loudness is obtained. Then tighten the locking screw.

3. The adjustments for the following are the same as above except for 2.1 and 2.7.

  1. Buzzer No.18A: Fitted in cordless P.B.X.S.
  2. Buzzer No. 21: Fitted in H.E.S. Telephones.
  3. Buzzer No. 30: Fitted in Bell Sets No. 39 and 44.

4. Tools Required

Pliers, Wiring, No. 2 For straightening striker shaft and for general use.
Screwdrivers Inst. No's 1 & 2 For general use.
Spikes capstan No. 3C   For adjusting screws when inaccessible with a screwdriver.
Spanners, Flat, No's 1 & 4 and 7 & 9 BA For general use.

REFERENCES:- E.I. TELES. Stns.A5201, E.I. TELES, Stns.A5201 and E.I.Teles, Stn. Q5001

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Last revised: October 30, 2022