RELAYS AND RELATED MECHANISMS 



(2) Check that the pressure of the brush wires on the sHp-rings is about 

 35 g wt. Adjust if necessary. 



(3) Set the wipers to contact 1, and adjust the armature stop until the 

 tips of non-bridging wipers He just behind the leading edge of the bank 

 contacts. 



(4) Set the pawl stop just touching the pawl. 



(5) Set the detent spring so that it fits snugly into the teeth of the ratchet 

 wheel. 



(6) Set the wipers to contact 25, and turn the bank adjusting nut until 

 the wipers again lie correctly relative to the bank contacts. Lock the nut. 



(7) Adjust both magnet adjusting nuts so that the operation of the 

 armature moves the pawl just more than one tooth, and so that both pole- 

 pieces are at the same height. Lock the adjusting nuts. 



(8) Ensure that the armature springs have sufficient tension to return 

 the armature positively. 



(9) Connect a self-stepping circuit, and adjust the interrupter contacts 

 for steady rotation. 



Mark 



An 



(a) 



A 



22V 



Input 



ilH 



Hf 



(c) 



Output 



Figure 34.31 Uniselector circuits: {a) homing; (b) drive to marked position; 



(c) count down by seven 



Uniselector circuits 



In this section three simple circuits are shown to illustrate the bases of 

 the common methods of uniselector operation. 



532 



