TRAFFIC CONTROL TELEPHONE SYSTEMS Circuit - Sam Hallas

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contact with the dome of the inner buffer, the clearance between the buffered
spring and the dome of the outer buffer to be 10 to 20 mil
7.3 The pressure required to separate the contacts with the buffered spring
resting on the outer buffer shall be 150 grammes minimum 250 grammes
maximum, measured at contact. (Readjust 160 grammes minimum 240
grammes maximum).
7.4 With the armature in the unoperated position, the combined pressure of
the two springs resting on the inner buffer shall be 10 grammes minimum
measured behind contact.
7.5 With armature operated the buffered spring shall rest on the dome of the
outer buffer with a pressure of 30 grammes minimum measured at the
contact. (Readjust 32 grammes minimum).
7.6 The contact opening shall be such that the electrical tests are met and the
contacts shall not be out of alignment by more than 1/4 diameter of contact.
8. Wipers
8.1 In positions No. 1 and 25 the line of contact of the nonbridging wipers
shall lie within the limits of 1/3 to 2/3 the width of the contact from the
entering edge. The centre line of the bridging wipers shall lie between the
centre line and the leaving edge of the contact, to be judged by the eye.
(The position on the first bank contact is obtained by adjusting the position
of the wiper assembly on the hub, on the 25th contact the adjustment
is obtained by adjusting the gland). When standing on the centre contacts
the centre of the crimp on non-bridging wipers and the centre line of the
contact area of the bridging wipers shall lie between the entering and leaving
edge of the bank contacts.
8.2 The tips of the bridging wipers when standing on any contact shall be not
less than 7 mil clear of the plane through the leaving edge of the previous
contact. This requirement also applies to wiper tips in the first position
after leaving the bank.
8.3 Before checking the wiper positions on any contact it is necessary to take
up any overthrow by lightly forcing back the ratchet wheel against thepawl
tip by hand. Force must not be used while making this check.
8.4 With the rotor assembly moved sideways in any position, no portion of
the wipers other than the tips shall touch the bank contacts.
8.5 When the wipers are clear of the bank contacts there shall be no gap
perceptible to the eye at the outermost contact points. Between the innermost
contact points there may be a gap not greater than 8 mil.
(Readjust 6 mil.)