Multi-beam shape auxiliary device for connection to a primary or secondary communication terminal (13, 113) of a multi-beam shape control device (M-RET), in particular for a mobile communications antenna system, comprising the following features: - the multi-beam shape auxiliary device comprises a site-sharing adapter in the form of a primary adapter, which is provided with a female or male connector configuration on the associated coupling terminal (KoAn) thereof, or in the form of a secondary adapter, which is provided with a male or female connector configuration on the associated coupling terminal (KoAn) thereof, - the site-sharing adapter comprises at least two primary terminals (A1, A2, A3) for connecting at least two primary control apparatuses, - the plug and/or terminal configuration or terminal assignment at the primary terminals (A1, A2, A3) is compatible with the terminal configuration or terminal assignment of the coupling terminal (KoAn) of the site-sharing adapter, - the connection pins or connection sockets, for example the connection pins/connection sockets 3, 5, on the at least two primary connections (A1, A2, A3), which pins or sockets are provided for the bidirectional signal transmission in the site-sharing adapter, are connected to a connection pin or a connection socket, for example a connection pin/connection socket 3, provided for bidirectional signal transmission, of the coupling terminal (KoAn) so as to form a bidirectional signal transmission path, - the bidirectional transmission path is configured such that the differential communication signals at the at least two primary terminals (A1, A2, A3) are converted into frequency-modulated signals, which are present at the coupling terminal (KoAn), the frequency-modulated signals present at the coupling terminal (KoAn) conversely being converted into differential communication signals which are present at the relevant connection pins or the relevant connection sockets 3, 5 of an associated primary terminal (A1, A2, A3). - the multi-beam shape auxiliary device comprises a site-sharing adapter in the form of a primary adapter, which is provided with a female or male connector configuration on the associated coupling terminal (KoAn) thereof, or in the form of a secondary adapter, which is provided with a male or female connector configuration on the associated coupling terminal (KoAn) thereof, - the site-sharing adapter comprises at least two primary terminals (A1, A2, A3) for connecting at least two primary control apparatuses, - the plug and/or terminal configuration or terminal assignment at the primary terminals (A1, A2, A3) is compatible with the terminal configuration or terminal assignment of the coupling terminal (KoAn) of the site-sharing adapter, - the connection pins or connection sockets, for example the connection pins/connection sockets 3, 5, on the at least two primary connections (A1, A2, A3), which pins or sockets are provided for the bidirectional signal transmission in the site-sharing adapter, are connected to a connection pin or a connection socket, for example a connection pin/connection socket 3, provided for bidirectional signal transmission, of the coupling terminal (KoAn) so as to form a bidirectional signal transmission path, - the bidirectional transmission path is configured such that the differential communication signals at the at least two primary terminals (A1, A2, A3) are converted into frequency-modulated signals, which are present at the coupling terminal (KoAn), the frequency-modulated signals present at the coupling terminal (KoAn) conversely being converted into differential communication signals which are present at the relevant connection pins or the relevant connection sockets 3, 5 of an associated primary terminal (A1, A2, A3).