Tandberg RC 20 Service Manual

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ransmitter - RC 207 Receiver - RC 20R Control operated Bit sequence at the output of Ul, pin 8 (transmitter) Logic levels at the outputs of Ul (receiver) ABCD Logic levels at connector pin No.: 12457 Wind and Rewind Stop Stop and Wind Stop and Rewind Stop and Play Rewind Record (both) Play Wind 1O ms approx. --{ IIIIII IIIIIIII I 0000 1000 0100 0010 1010 0110 0001 10110 11011 01110 11110 11101 11001 10111 It LI Table 1 -1 =Q Receiver unit RC 20R Functional description The receiver has two main functions: - One function is to convert the IR light from the transmitter to electrical signals which operate the tape deck according to a system of command signals. - The second function is to select (with the aid of other controls) whether the tape deck goes over to Play or Record when a Timer is used. A Timer switches on the power to the tape deck automaticalll' at a chosen time. E lectrical description - The IR amplifier is located on the top circuit board (A2-1) in the receiver unit. - The receiver diode CR1 is very sensitive to IR light and the diode is equipped with an optical filter which makes it insensitive to visible light. The circuit is designed to suppress i00/120 Hz light from incandescent lamps. This is important since tape decks are often used near to strong artificial light. An incandescent lamp radiates 30% of its power within the sensitive spectrum of CR1.