The guaranteed transmission of launch order signals to SSBNs on patrol at sea is supported by transmitting them over a group of frequencies including not less than 2 frequencies for very long waves (VLF), 5 short wave frequencies (HF) and 5 space lines of communications. The transmission of the signals is continuous in relation to the given schedule for communications with SSBNs.
Electromagnetic waves on the extremely low frequency ( ELF), a frequency of several tens of hertz, in distinction from the shorter electro-magnetic waves possess the advantage that they may penetrate to depths of up to 200-300 m. The signals of the ELF station "Zevs" which is located on the Kola Peninsula, may be sent to strategic submarines in practically any area of the globe. Since the speed for transmitting information on the ELF channel is very low, only general commands for all SSBNs on combat patrol are sent. These commands are designated ahead of time by a fixed code. For example, with separate codes one may designate the order: "Approach the surface to receive order to use weapons" or "bring to full combat readiness" During peacetime the ELF channel continuously transmits the code. That means "the situation is normal". Breaks in the transmission of this code is a signal that an "extreme situation" has been established.
Very long frequency (VLF) signals may penetrate water at depths of up to 20 m. To receive these signals submarines must rise to periscope depth or deploy their swimming receiving antennas. To provide communications on large parts of the world's oceans (except the remote waters of the southern hemisphere, the western part of the Atlantic and eastern part of the Pacific ocean) five permanent VLF stations were working on the USSR's territory and were located in Molodechno, Nizhny Novgorod, Tashkent, Krasnodar and Khabarovsk. These stations are presently functioning and are continuously broadcasting on five frequencies from 3 to 30 kHz. VLF channels are used to transmit not only general orders for all SSBNs, but also combat control signals, which constitute the release codes for launching missiles and accompanying information.
Mobile coastal and aviation VLF stations are intended for relaying orders for using weapons under combat conditions when there is a great possibility that the enemy has taken stationary transmitters out of service. To do this, the USSR created the TU-142 RTs airplane, which went into military service in 1985. The length of the transmitting antenna of this airplane reaches several kilometers. During threatening periods communication aircraft carry out "buzzing" in the regions where SSBNs are patrolling. At the end of 1992 there were 13 TU-142 RTs aircraft in Russia, seven of which were stationed in the Pacific Ocean Fleet and six in the Northern Fleet.
The network for short-wave and VHF radio communications is the most diversified. It includes a multitude of stationary and mobile ground transmitting centers and radio relay stations. This network also includes satellite, aviation and ship-board relays. At the dawn of the strategic fleet, short wave communications were the only means for transmitting operational information to submarines, which carried out military duty off the US shores, as well in the Atlantic and Pacific oceans.
The basic insufficiencies of HF and VHF band radio waves are that they do not penetrate deeply into water. To receive HF and UHF signals submarines rise to periscope depth and deploy a telescopic antenna above the water's surface. Modern submarines are also equipped with floating towed antennas. This allows the submarine to receive information while located at depths of up to 120-150 m from the surface. Nevertheless, a metallic antenna on the water's surface represents a vulnerable target for the enemy's radars and may be detected at distances of up to several tens of kilometers. Due to the great speed for transmitting information and comparative cheapness and convenience of using HF and UHF communications, it is the basic means for operational control of SSBNs in peacetime.
The fact that sound propagates in water at great distances served as the basis for creating not only acoustic systems for detecting submarines, but also systems to communicate with them. The basic advantage of acoustic communications is the absence of the need for a submarine to surface and use towed or telescopic antennas. Due to these advantages channels for underwater sound communications are frequently used in combination with radio communication channels. Thus, in regions where submarines patrol, there may be a near-bottom fixed station for underwater sound communication, which unites ships with coastal points relaying radio signals. Underwater sound communications are also convenient for joint tactical actions of submarines with other submarines and surface ships.
The problems with this type of communication are the significantly smaller
speed of sound propagation in water in comparison to the speed of radio
waves and the strong absorption of sound at frequencies, which support
acceptable speeds for transmitting information (several tens of kilohertz).
Therefore, the underwater communication sound system is used to transmit
signals only for comparatively short distances (up to 10-30 km).