5 Nominal contact wire height [N.NN] Nominal value of the contact wire height at a support in the normal conditions expressed in meter.
https://www.google.de/?gws_rd=ssl#q="Nominal Pull Value" "ov...

In order to make electric locomotives by the good contact between the pantograph and overhead contact lines, and ensure that there is proper contact force, for the highly electrified railway overhead contact lines have certain requirements, the height of (6000 ± 30) mm. Meanwhile, in order to make electric locomotive pantograph contact skateboard wear uniform, overhead contact lines required by the "s" shaped placement, it has two rail centerline to the pantograph "" shaped pull out values have certain requirements, "the" Pull out the value of the glyph is generally (480 ± 10) mm.
http://www.google.com/patents/CN2625843Y?cl=en

In the electrified railway power supply system, electric locomotive obtains power from the catenary's wire through the pantograph. Under the action of the pantograph, combined with various factors such as vibration, touch current, relative sliding speed, load, etc, the contact wire will produce mechanical wear and electrical wear. Thus, in electrified railway construction and daily operations, the geometric parameters such as line height, pull value, the width of wear surface must be under real-timely and non-contact detection.
http://adsabs.harvard.edu/abs/2010SPIE.7656E..80P

Measurement of the geometric parameters of power contact wire based on binocular stereovision
:
Thus, in electrified railway construction and daily operations, the geometric parameters such as line height, pull value, the width of wear surface must be under real-timely and non-contact detection.
http://proceedings.spiedigitallibrary.org/proceeding.aspx?ar...

According to the technical requirements of the contact line must be positioned. Anchor point and the center of the locomotive pantograph slide a certain distance, the distance in a straight line segment called "the" word values; in the curve section called Pull value. Generally referred to pull the value represented by a. According to the Ministry of Railways issued Order No. 1, "Railway Technical Management Rules) provides: straight sections, the center line coincides with the locomotive by the pantograph center, pull out the value of the center along the road layout, the standard is ± 300mm; pull out the value curve segments criteria in Table I.
http://www.google.com/patents/CN2217214Y?cl=en
Note: All relevant patents mentioning “pull value” or “pull-off” come from China.

Contrepoid de tension (caténaire)
Counterweight {pull-off Am} for tightening overhead contact line
(Lexique général des termes ferroviaires)

http://de.wikipedia.org/wiki/Oberleitung

To achieve good high-speed current collection, it is necessary to keep the contact wire geometry within defined limits. This is usually achieved by supporting the contact wire from a second wire known as the messenger wire (in the US & Canada) or catenary (in the UK). This wire approximates the natural path of a wire strung between two points, a catenary curve, thus the use of "catenary" to describe this wire or sometimes the whole system. This wire is attached to the contact wire at regular intervals by vertical wires known as "droppers" or "drop wires". It is supported regularly at structures, by a pulley, link, or clamp. The whole system is then subjected to a mechanical tension.
:
… On straight track, the contact wire is zigzagged slightly to the left and right of centre at each successive support so that the pantograph wears evenly. The movement of the contact wire across the head of the pantograph is called the 'sweep'.
http://en.wikipedia.org/wiki/Overhead_line

La régularisation est le maintien de la tension mécanique du conducteur.
La présence de contrepoids, destinés à maintenir une tension mécanique constante dans la caténaire (généralement, pour une plage de régulation de 70 °C, s’étendant de --20 °C à +50 °C), n’est pas systématique. En effet, en 1 500 V continu notamment, les tirs des caténaires simples (CS), légères (CL) ou de type « fil tram » (un seul ou deux fils de contact, sans porteur ; on parle alors de « LAC » pour Ligne Aérienne de Contact) sont directement ancrés aux supports, sans contrepoids, car la vitesse peu élevée des véhicules permet de compenser au sein du pantographe les différences de hauteur du câble, sans entraîner de chocs sur le câble ;
Positionnement latéral
Vu de dessus, le fil de contact d’une caténaire ne forme pas une ligne droite, mais un zigzag. Cette disposition est destinée à éviter l’usure ponctuelle de l’archet du pantographe.
Le positionnement latéral du fil de contact est généralement assuré par des bras de rappel montés sur des armements caténaires.
http://fr.wikipedia.org/wiki/Caténaire#R.C3.A9gularisation

The page holder keeps the contact wire clamp and thus the contact wire in the specified side.
http://www.google.com/patents/WO2000013929A1?cl=en

Beruehrungslosen pave means for measuring the height-and lateral position of the contact wire in electrical
http://www.google.com/patents/DE2440085A1?cl=en

5 Overhead contact system according to claim 4, characterized in that, for greater maximum permissible change in length of the lateral position of the line laid in a zig-zag line is smaller.
http://www.google.co.ug/patents/WO2010012517A1?cl=en&hl=de

1 Send a measuring device for determining the lateral position of a contact wire for electrically operated rail vehicles by spot sensing the position of the contact wire …
http://www.google.com.vc/patents/DE20213180U1?cl=en