Telephone pole

Telephone pole with isolators in Switzerland

Mast with telephone box of the line telephone line on the Preßnitztalbahn

A telephone pole (often called a telegraph pole ) is a pole that carries telephone lines laid above ground . Telephone poles are mostly made of wood . They can be in use for 30 years or more.

Areas of application

Since 1852, when the Prussian Telegraph Administration established the first above-ground telegraph line with wooden masts, wood has remained the dominant material in above-ground line construction, which can be attributed to the following reasons:

The coniferous wood of the wooden poles has a very high load capacity with low weight,
Wood can be easily processed with a saw, a wood drill and the wood adze ,
In a cost comparison with other materials (concrete, iron, plastic), the price of a wooden pole is the lowest at around 50 euros (as of 2002).

The disadvantage that arises from the fact that wood comes from organic nature, i.e. has to be protected against fungal attack, insect damage and other destructive organisms, can be prevented by appropriate impregnation processes. The empirical values for some impregnation processes are as follows:

Pine and larch woods that have been impregnated in a tar oil boiler pressure process have an expected service life of at least 30 years, for spruce and fir wood impregnated with a chromium-arsenic-containing salt mixture, a service life of around 20 years can be taken as a basis.

A telegraph pole in the Odenwald was part of an above-ground line association for 100 years. It belonged to the earlier telegraph line Führt - Erbach , which was put into operation in 1868.

In the public telephone network of Central Europe, only isolated telephone cables that contain several lines are laid on telephone poles . Such a cable is called an aerial cable .

Telephone lines with bare wires ( overhead lines ), however, are no longer used in the public telephone network in Germany and in many Western European countries. A telephone connection requires two wires.

The last telephone lines with bare wires in the public telephone network were probably replaced by aerial or underground cables in the old federal states in the second half of the 1970s, in the new federal states around 1999 . However, no date can be determined for the dismantling of the last overhead telephone line in the public telephone network in Germany.

Along the non-electrified branch lines of the railways there are occasionally masts of the mainline telephone lines , but they are increasingly being dismantled with the introduction of GSM-R .

crampon

Mast crampons and belts for telegraph poles made of wood

Telephone poles are climbed with the help of special crampons . These crampons have a semicircular stirrup that runs to the right on the left crampon and opposite on the right. Furthermore, a special belt is required to climb a telephone pole . Two lines are attached to this belt , which are placed around the mast and fastened back to the belt with the aid of snap hooks . This belt prevents the climber from tipping over backwards. Furthermore, the climber can lean back at the upper end and work comfortably. The safety equipment (belt) only had to have a leash with a snap hook until 2004. These belts were changed because of the following problem: At least two masts (mast 0 and the last mast, sometimes also in between) of an above-ground line have a strut that converges with the mast at the upper end. This makes it necessary to briefly take off the safety line in order to place it over the crossbar. It has occasionally happened that when the snap hook was hooked into the belt, it was not properly closed or that the climber fell before hooking the snap hook into the belt. In order to avoid this, the safety belt was equipped with two safety lines. A line can be placed over the strut while the climber is always secured. Furthermore, a mast may only be climbed if a second employee / colleague is on site who can help in an emergency . The crampons remain firmly anchored in the mast, even if the climber tips over backwards.

Marking in Germany

Designation pins on a mast in Germany

Data matrix code and anchoring point number on a mast

Marking according to EN 14229 on a mast

Since 1964, the masts have been typed with three to five designation nails. With three nails, the triangular one indicates the type of wood (1 = pine) and the manufacturer. The first digit on the square mast nail indicates the impregnating agent, the other digits the impregnation method. The drinking system and the year of drinking are noted on the round.

According to DIN EN 14229 “Wooden structures - wooden masts for overhead lines”, however, this information is no longer sufficient. A new, uniform sticker was therefore defined, which contains the required minimum details and further information. These include, for example, the CE mark and the number of the EC certificate of conformity, the name and logo of the mast supplier and the abbreviations for the type of wood and impregnation agent.

The German Telekom characterizes their telephone poles today with anodized aluminum plates on which a data matrix code and seven-digit number printed on it. The code then refers to the actual information within a database. By 2016, 3,250,500 labels were to be attached to all of Deutsche Telekom's wooden poles. According to Deutsche Telekom, it still has more than three million wooden poles in its portfolio in 2016, on which more than 100,000 kilometers of above-ground lines run.

Disposal as hazardous waste

Telephone poles were typically impregnated with carbolineum (black mast), more rarely with arsenic salt (green mast), which makes them extremely weatherproof and durable. However, this impregnation is toxic ( carcinogenic ) to humans and direct skin contact with telephone poles should be avoided. For this reason, old telephone poles are to be disposed of as hazardous waste and, in particular, must not be burned or used to build toys or playgrounds .

literature

Johann Deuringer: 150 Years of Above Ground Lines - Part 2 ; in: Deutsche Telekom class sheets - Deutsche Telekom's trade journal for training and further education; 55th year, issue 9; September 10, 2002, pp. 452-463
Telecommunications Technology Handbook - Volume 7 Part II - Line Technology - 1973 (PDF)
Handheld dictionary of electrical telecommunications ;
- 1st edition; Volume 1 A-K; P. 142 (»Identification nails«)
- 1st edition; Volume 2 L-Z;
  - »Mast foot« → »pole foot«; P. 536
  - »Mast isolator«; P. 88
  - »Mast protection« → »Pole protection«; P. 557
  - "Support post"; Pp. 580-581
  - »Support pole for overhead lines«; P. 581
  - »Support point distance«, p. 581
- 2nd Edition; Volume 3 Q-Z; P. 1620–1621 (»Support points for above-ground lines«)
Instruction sheets of the Deutsche Bundespost
- The wooden mast; 1955: issue 13; Issue 14 p. 163; 15; 16/177; 17; 18/202; 19, 20/219
- Digging and drilling equipment for making the mast holes and the use of the auxiliary anchor in telecommunications; 1959: issue 5/95
- The wooden mast in 1963; 6/159, 8/225, 10/285, 11/333, 12/373
- The wooden mast 1964; 1/9
- Wood protection of telecommunications masts 1978; 5/141
- "150 Years of Above Ground Lines - Part 1", Instruction Sheet No. 8/2002, pp. 384 to 399.
- "150 Years of Above Ground Lines - Part 2", Instruction Sheet No. 9/2002, pp. 452 to 463.