طرق تلحين (توليف) الناخب ١_a ..كتاب التلفزيون الملون والعادي

5-9 Methods of Tuning the Voter:

There are several ways to tune the voter to a particular channel. All are based on the principle of a resonant circuit consisting of a file and a capacitor, as in a radio. These are the ways:

​​​​​​1 - Mechanical method: by means of a rotary switch that has positions in the number of channels that can be received (12) positions, and it has two types:

A - Slide type (tower): Each channel has one slide that moves with the internal section of the switch, and it is of latex. It has four coils connected to eight contact points, and they touch fixed contact points to complete the circuit. It is provided with a key for fine tuning in the center of the rotary switch numbered with channel numbers. This type has mechanical and electrical disadvantages, as it is subject to looseness, weakness, and corrosion of the contact points. Or a fracture in the flexible pieces in the voter, and Figure (5) - (27) shows the parts of the tower voter
B- Disk type: These discs are fixed to the axis of rotation (Fig. (5-28) and there are four of them that include the following tuning circuits: the input circuit of the radio frequency amplifier - the circuit of the output of the radio frequency amplifier - the circuit of the oscillator - the circuit of the mixer. Only three discs can be used if they are combined The circuit of the radio amplifier with this type the output of the mixer -
The same disadvantages of the previous type, but it is characterized by the fact that the second contacts are less, and this type has spread more than the previous type - but it has begun to decline in front of the voter

electronic.

2- The electronic method of tuning the voter: which is recently applied in colored and monochromatic devices. It depends on the principle of the capacitive diode (Fractur), which changes its capacitance according to its polarization voltage and inversely proportional. That is, its capacitance decreases as the continuous reverse voltage applied to it increases. Multiple diodes can be made in one piece. By changing the amplitude of the diode, the resonant frequency changes, and it is tuned to the desired station, as in circuit (5) - (29), and these devices include a number of pistons 6 - 12, and any of them can be tuned by the tuning button after selecting the station field. VI ni or UHF, VHF, and the selection of the station may be by touching the channel number, or electronically via a remote control (remote control). - 32 (e - 33) shows a complete diagram of an electronic voter. A transistor voter model for a 26-inch color TV Seronix with an electronic tuning circuit with capacitive diodes - and the touch method is used to select
the channel .