Located to the southeast of the centre of Sant Salvador de Guardiola, near the new Brunet House. The Brunet tower was a military optical telegraphy tower. The building has the classic typology of this type of construction. It was square in plan and had a rectangular defensive body attached to the north face, and was surrounded by a moat. In elevation, it consisted of a slightly embattled ground floor with four loopholes on each side, an upper floor with loopholes and windows, and finally a roof terrace (partially in ruins). The entrance door opened at the height of the first floor on the south side, probably accessed by means of a wooden staircase that was kept inside. The walls are made of rusticated stone masonry and the division between the floors is marked by a protruding profile.

The Brunet tower was part of the Barcelona-Manresa-Solsona military optical telegraphy line. This line shared the first seven telegraph towers with the Barcelona-Lérida line. Thus, the line began at the tower of Montjuïc Castle and continued to the tower of Can Maçana or La Guardia, in the village of El Bruc. It then turned north towards the Brunet tower. The Brunet tower, 420 m high, had a direct line of sight to the previous tower of Can Maçana del Bruc, located 7.4 km away to the south. The rear tower was Puigterrà de Manresa, 6.8 km to the north (no longer standing). The later tower preserved in the latter is that of Sant Martí de Torroella in Sant Joan de Vilatorrada.

The Brunet tower was part of the Barcelona-Manresa-Solsona military optical telegraphy line.

Optical telegraphy is a system based on a series of signals made at a high point, such as a tower or a bell tower, by an operator, which another operator sees from another point, communicated visually, and repeats it; in this way a message can be transmitted quickly from one point to another on the line. There were various ways of making the signals, such as a tall wooden pole with two crossbeams at the ends which, operated by pulleys, could change position – each position was a letter or key which, thanks to a book of keys, could be deciphered. The operators had long-sighted glasses that allowed the distance between the different points to be greater than if they did not have them.

While in countries such as France and England optical telegraphy lines had already been built at the end of the 18th century, in Spain construction did not begin until 1844, by which time electric telegraphy had already begun to be used in some countries. The creation of a line involved the installation of communication systems on existing high points or the construction of towers in places where the distance was too great.

In Catalonia, the first line came from Valencia and reached La Jonquera via Barcelona. During the Second Carlist War (1846-1849), the Marquis of Duero, Captain General of Catalonia, commissioned the development of an important military fixed optical telegraphy network. Six lines were created, including the Manresa - Vic - Girona line.

In 1853, the first electric telegraphy line was built between Madrid and Irún, which marked the beginning of the abandonment of optical telegraphy and the disuse of the towers built for this purpose. In 1857, the civil telegraphy towers were dismantled and abandoned, and in 1862 the military towers were officially abandoned. This marked the end of the short history of optical telegraphy in Catalonia, but which left the telegraph towers as a witness.