Now a lot of control with the lower prices with the lens in your store, office or home to install a surveillance system to become more practical. However, you may have to consider for each surveillance camera with a monitor device, or buy a single display can simultaneously display more than one monitor screen dedicated Monitors. These methods, their input will be relatively large. Here a video switcher can be made (see Figure 1)

It uses video switch ASIC, can be two, three or four shots of the monitor screen displayed on a monitor in turn. The number of the lens to switch the circuit board by the DIP switch settings. In automatic mode, the switching speed of the lens on the front panel knob can be from 1 to 20 seconds to adjust. Manual mode, all the way to monitor the camera image can be fixed on the monitor, and one by one by manually controlled trigger switch to switch the control lens.

Circuit shown in Figure 2. Circuit is the core of a video switching circuit MAX454 (see Figure 3). It has good quality images and low output phase distortion characteristics. Internal circuitry includes 4 video inputs (IN0 ~ IN3) and a low input impedance of the line amplifier, driver, two address inputs (A0, A1), a video output and two power terminals. Surveillance camera through the J1-J4 and switch video input Duanxiang together. Constitute the input resistance 75O termination resistors. The internal gain of the amplifier 13 by a pin connected to IC1 feedback network settings. Feedback network consists of R5-R8 and C3 form. The gain setting of 2 is to compensate for the terminal resistor R9 (75O) on consumption. Finally, the gain of the output is 1 J5.

Figure 3
  IC2 (CD4017, decimal notation, distributor) component video switching circuit. When a clock pulse input from 14 feet, Q0 ~ Q4 will turn out high (see Figure 3). D1 ~ D4 and IC2 of the three outputs (2,4 and 7 feet) constitute ten to binary conversion circuit, IC1 to provide the address for the code. T1 ~ T4, respectively, while the 3,2,4 and 7 with the IC2 pin linked to drive LED1 ~ LED4 as a lens to switch directions. R15 for the light-emitting diode current limiting resistor. Surveillance camera set by the DIP switch number S1 decision. Such as: If only two surveillance camera associated with the switch, S1-a should be connected, then the output of IC2 and the first reset terminal 4 (15 feet) is shorted. When IC2 count to Q4 (10 feet) output, this high level through the S1-a to reset IC2, so switch back to the first surveillance camera. This circuit will be between the lens 1 and lens 2 cycle. Similarly, switch S1-b, or S1-c 3 or 4 can change the lens.
  IC3 (LMC555) constitute a clock pulse generator for counting pulses provided IC2. R12 output frequency adjustment from 1 to 1/20Hz. S2 for the single-pole three-throw switch. Playing in the automatic position, IC3 pin 3 output count pulses through S2 into the IC2 input clock pulse (14 feet) to the circuit automatic counting, cycle switch. When playing to the manual position S2 (S2 is the switch with a spring return), the supply voltage to IC2 by a count of S2 pulse, to achieve manually switch each lens. When the S2 in the middle position, IC2's R13 count input is set to low, counter does not work.
  Power in part by the T1, IC4, IC5, and D5, D6 and C6 ~ C9 form ± 5 V power supply.
  Since high-frequency circuits for processing the video signal, we should pay attention to in the production of printed circuit boards will need to adopt, if you own design circuit boards, please pay special attention to the signal ground terminal foil around the protection required to prevent the introduction of noise and crosstalk . When installing the components, it is recommended welding resistance and diode, and then cut the front part of the lead used two jumpers. Followed by S1 and IC2, IC3 socket, but do not use the socket IC1. J1 ~ J5 installed, if the point with a power larger electric iron would be better. After this is Q1 ~ Q4 and capacitor and LED1. Finally, IC1 soldered directly to the circuit board, and pin as short as possible signaling leads to benefit.
  In addition, similar to the manifold with the MAX452 function also MAX453 (two), MAX455 (eight), with its direct access to more information MAXIM website (www.maxim-ic.com), both in the search column input MAX454 All relevant information available, and may request free samples of the experiment.