What is stereo?
There are now two system of high fidelity, monophonic (monaural) and stereophonic. Monophonic is a system that starts from one microphone and is fed through a single high fidelity set. Stereophonic is a double system. Two separate microphones are placed at different sides of the orchestra and two different systems are used to keep the two signals or channels separated. Two separate speakers are used, placed on different sides of you room. Stereo is much like 3-D photography, two slightly different sound reach your ears giving you a new dimension in sound.
H.H. Scott '59
- The receiver consists of a PIN photo diode, amplifier, LC tuning circuit, detection circuit, and wave-form shaping circuit (Schmitt Trigger), and it changes the infrared signal from the transmitter into the original 10-bit signal.
- The 10-bit pulse signal is processed by the microcomputer, and then the necessary remote control signal is taken out from each output port.
- The output interface is a circuit to facilitate the conection with each equipment, and it is an inverter using an open collector.
- MN6025C is an 5-bit IC which can generate 25 kinds of signals. The oscillation frequency is 396 kHz and is divided by 12 to obtain 33 kHz which is used as modulation frequency. It is further divided by 16 to achieve 2,06 kHz which is the clock frequency of this IC.
- When the keyboard is depressed, Mn6025C starts oscillating and generates series pulses of 5 bits plus inverse 5 bits, totalling 10 bits, according to the key position.
- The 10-bit pulse signal is modulated by 33 kHz carrier.
- The modulated signal from MN6025C is applied to the infrared LED and command eye LED drive circuits. With oscillation time is about 60 msec. required for 10 bits, while the lighting up time of the command eye is set at about 0,5 sec.
- In this control, five attenuators of -2 dB, -4 dB, -8 dB, -16 dB and -32 dB, and a muting circuit of -20 dB are turned On-Off by an analog switch for changeover in 32 steps renging from 0 dB to -6 dB and to ∞ by -2 dB each.
- The analog switch is driven by a 5-bit binary up-down counter, which is provided with last sound function due to the back-up signal from the tuner pre-amplifier.
- The volume control up-down switch gains 1 step in the initial 0,5 sec. of push, and keeping it depressed causes step-by-step volume control every 0,15 sec. When the switch is kept depressed, it takes about 5 secondes for the change from 0 dB to -∞ dB.
- A 5-bit IC (LC7500) is used as the controller for the electronic volume. With this IC, the five attenuators can be selected in 32 steps. The internal oscillation frequency 800 Hz is divided into pulses of 0,15 sec. period, and the pulses are counted at the counter circuit to select the attenuators.