Jun 26
Circuit consists of following stages.
1. Microcontroller
The heart of the system is Atmel AT89S51 microcontroller which is running on 12 MHz clock speed.
2. Power Supply
The main power source is 220V AC, which is step-down into 24V and 72V. The18V DC is used for telephone system and 72V AC supply is used for ringing telephone bells which is controlled by RL10.
3. Ring Detector
This stage converts the incoming bell signals into pulses. These pulses are counted by Timer1 in the micro controller. The system hold the (Outer) call after two bells, two bells have 37 pulses.
4. Tone Generator
This stage consists of CD4093. The gate A oscillate on 440Hz and gate B oscillate on low frequencies then gate C “AND” the output of A and B gate. This arrangement is done for generating dial tone and busy tone. Gate D generate dial tone, dial tone is controlled by P3.6 and busy tone is controlled by P3.4.Dial tone is provided to speech bus and busy tone is provide on standby bus.
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Jun 25
An RFID system consists basically of two compo-
nents:
Transponder
(fixed on an object that shall be identified)
Reader
(or interrogator base station)
A transponder includes the IC, and in LF systems
optionally a capacitor and a coil. HF systems only
need a coil, UHF systems an antenna. The reader
generates an RF field which is used to transmit
power and to per form bi-directional, contactless
data transmission (no connection or line-of-sight
necessary). As soon as a transponder or smart
label gets into the field generated by the reader, the
tag transmits information either immediately or on
request only. The reader decodes this information,
sends it to a host, or displays it.
RFID Applications
Versatile and flexible products form an Atmel prod-
uct scope that offers solutions for almost all appli-
cations in the main RFID market segments. Atmel’s
products fulfill the market requirements that call for
fast, secure and reliable identification systems.
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Jun 25
ASTM Format
Analyzers format responds to the ASTM specifications E-1381 & E-1394:
• E-1381: Standard specification for Low Level protocol to transfer messages between
clinical or laboratory instruments and computer systems.
• E-1394: Standard specification for transferring Information between clinical or
laboratory instruments and computer systems.
1. Connection specifications (ASTM E-1381)
1.1. Hardware and software characteristics
You can setup Baud rate, Parity, Stop bit,…
Hardware setting of the interface: Connect the Host and the instrument by the DB9 serial
port.
1.2. Output data characteristics
Characters: ASCII
Maximum message length: 247 characters.
Analyzer manages Xon/Xoff protocol.
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Feb 24
The ATA8203/ATA8204/ATA8205 is a multi-chip PLL receiver device supplied in an SSO20
package. It has been specially developed for the demands of low-cost RF transmission systems
at data rates of 1 kbit / s to 10 kBbit / s in Manchester or Bi-phase code. Its main
applications in the areas of aftermarket keyless entry systems and tire pressure monitoring
telemetry systems, / remote control applications for industrial consumers, home entertainment
systems, access control and security technology systems. Can be used on the receive frequency of
range of f0 = 312.5 MHz to 317.5 MHz, f0 = 431.5 MHz to 436.5 MHz or 868 MHz to f0 =
870 MHz for ASK or FSK data transmission. All statements below refer to 315 MHz,
433 MHz and 868.3 MHz applications.
The PLL generates the frequency of the FLO unit for mixer using a fully integrated synthesizer with
low-noise integrated LC-VCO (Voltage Controlled Oscillator) and PLL-loop filter. The XTO (crystal
oscillator) generates the reference frequency FREF = fXTO / 2 (868 MHz and 433 MHz versions)
or FREF = fXTO / 3 (version 315 MHz). The integrated LC VCO generates two or four times the
frequency mixer unit fVCO. The I / Q signals for the mixer are generated with a divide by two or
four circuit (OLF = fVCO / 2 for the version of 868 MHz, FLO = fVCO / 4 to 433 MHz and 315 MHz versions).
fVCO is divided by a factor of 128 and 64 and is fed into a phase frequency detector and compared
with FREF. Output of phase frequency detector is introduced into an integrated circuit filter
and therefore generates the control voltage to the VCO. If it is determined FLO fXTO can be calculated
using the following formula:
FLO/128 FREF = 868 MHz, FREF = fLO/64 for 433 MHz fLO/64 FREF = 315 MHz
bands.
download data sheet [link]
