The MP-8 "Sigma-RA" device is designed to protect a telephone set in call waiting mode from leakage of room signals in the audio frequency range through an analog telephone line. Information leakage from signal sources due to acoustoelectric transformations, as well as information retrieval using active methods of influence, is excluded.
The fundamental qualitative difference of the MP-8 "Sigma-RA" protection device is the complete galvanic isolation of the telephone set (TS) from the subscriber line in call waiting mode.
The MP-8 "Sigma-RA" device is structurally designed as a separate unit and is installed near the TS in the break in the telephone cable, while the MP-8 device is connected to the TS with a short (25 cm) end of the cable, and to the telephone line (TL) socket - with a long cable (1.5 m) from the delivery set.
The MP-8 device contains an autonomous calling device (ACD), which in the "CALL" mode sends an audio and duplicate optical signal (green LED). The call signal from the TL is sent to the ACD via an optoelectronic isolator (OPI), which ensures the transmission of the information signal in only one direction - from the TL to the telephone set.
In the "CALL WAITING" and "CLEAR DOWN" modes, with the telephone handset on the hooks, due to the corresponding switching of the contacts of the electromechanical relay (ER), the telephone set is completely galvanically disconnected from the TL, while no electrical signals pass from the telephone set to the line or from the TL to the device. When the telephone handset is lifted from the ACD in response to the signal from the ACD or to dial the desired subscriber, the ER contacts automatically connect the telephone set to the TL, ensuring the "CONVERSATION" mode.
The product is certified by the FSTEC of Russia and can be installed in dedicated premises up to and including category 1.
Specifications: Input electrical resistance module in the mode: - conversational is determined by the type of the connected telephone set - call waiting infinity - call not less than 14 kOhm Current consumption from a 12 V battery in the mode: - conversational 0 mA - call waiting 0 mA - call not more than 5 mA - dialing not more than 3 mA - with the line disconnected, the telephone connected and the handset lifted not more than 30 mA Direct current consumed from the line in call waiting and hang-up mode 0 mA Alternating current consumed from the line by the calling device not more than 3 mA Called signal level at a distance of 0.5 m not less than 83 dB Mean time between failures not less than 100,000 h Device dimensions not more than 105 x 74 x 26 mm Weight not more than 120 g