Traditional Chinese Practical Protective monitor: Circuit Design, Parts List & Workshop Prototype Guide
In short: Traditional Chinese Practical Protective monitor. This entry documents a circuit & prototype taken from Chinese practical-technology literature, written for small-scale makers and home producers. The text below is the full English translation of the original Chinese workshop notes, covering materials and quantities, the step-by-step sequence, and the practical cautions recorded in the source. Roughly 2575 words of English technical text, translated and preserved without editing. It is intended for experimental and reference use, not for regulated or commercial certification.
Protective ListenerThe listening distance of the protective monitor can reach 100m without an antenna, and it can work continuously for 5 to 6 days using a 3V chip button battery. It is suitable for baby cry monitor monitoring, anti-theft monitoring, outside door monitoring and other occasions. Its size is only the size of a large button and is very convenient to use.The schematic diagram of the monitor circuit is shown in Figure 205. It uses a BP electret microphone to pick up nearby sounds and convert them into audio electrical signals. This weak audio electrical signal is amplified by an audio amplifier composed of transistor VT1 (9013) and other components, and then coupled to the high-frequency circuit via C2 for frequency modulation. After the high-frequency signal modulated by the audio signal is emitted, it is received by the FM radio in the distance and the sound is restored. The operating frequency range of the high-frequency circuit is between 82 and 108MHz. The frequency is determined by C4 and L1. The operating frequency can be changed by changing the capacity of C4 or lengthening or shortening the distance between L1 coils. The operating voltage of the circuit is 3V, the operating current is less than 1mA, …
Sign in to unlock
One-time payment per article, billed in credits (1 $ = 100 credits). You will review the invoice and the non-refundable digital-asset policy before anything is charged. The PDF is generated on demand and embeds a licensing watermark.
Unlock this article
One-time payment · permanent access after unlock · 1 $ = 100 credits
Member level pricing for this article
| Level | Cumulative top-up | Discount | Your price | You save |
|---|---|---|---|---|
| Free | Free | — | 4,278 credits | — |
| Bronze | $100.00+ | 2% off | 4,192 credits | 86 credits |
| Silver | $1,000.00+ | 5% off | 4,064 credits | 214 credits |
| Gold | $5,000.00+ | 10% off | 3,850 credits | 428 credits |
| VIP | $20,000.00+ | 15% off | 3,636 credits | 642 credits |
Prices are billed in credits (1 $ = 100 credits). Your level upgrades automatically as your cumulative top-up grows. Top up to unlock a higher discount ›
All articles are digital assets. Once a PDF is downloaded, the purchase is final and non-refundable.
Please log in to unlock this article.
Payment Methods
pay@viprole.com
Lei Cheng
pay@viprole.com
Lei Cheng