In the 80~90s, the legendary Motorola had two treasures, one was Big Brother, which we had disassembled in the last issue; The second is the BP machine, because after the message will make a "beep" sound, slowly called it BB machine, Chinese also called pager. This issue of the hardcore teardown review will disassemble a Motorola pager to see what hardware such a revolutionary product was made of at the time? How does it work?
dismantle
THE BB MACHINE IN MY HAND IS A MOTOROLA ADVISOR VERSION, WITH A SMALL SCREEN AT THE TOP, A KEYBOARD BELOW, AND A BATTERY COMPARTMENT AT THE BOTTOM, AND THE PRODUCT IS MAINLY MADE OF PLASTIC, WHICH IS QUITE LIGHT IN THE EYES OF THE TIME. The family portrait after dismantling is shown in the figure below.
When disassembling, you will find that the design structure of this pager is still very amazing, without a single screw, all rely on the structure to combine it. In addition to the external structure, the main hardware consists of two PCBs, which can be roughly divided into a receiving circuit (small board) and a decoding circuit (large board).
The hardware of the receiving circuit (small board) includes antennas, amplifiers, mixers, oscillators, crystal filters, ceramic filters, intermediate frequency demodulators, voltage regulators, etc.
From the perspective of specific functions: antennas and amplifiers mainly receive, amplify and filter RF paging signals; The mixer converts the RF paging signal into an IF signal; The quartz crystal filter attenuates the upper and lower edge frequencies of the carrier frequency signal; The oscillator provides the appropriate RF signal for converting the RF paging signal into the correct IF signal; The IF demodulator amplifies, filters and mixes the IF signal to produce a second IF signal of 455kHz, and demodulates it to recover the data; The receive circuitry also includes circuits such as voltage regulators, current references, and under-battery detection.
The main functional hardware includes linear holding components (U4), CMOS holding components (U2), microcontrollers (U1), I/O expansion components (U6), RAM, ROM, voltage expansion components (U7), displays, etc.
The main functions of each section are as follows: The linear hold component provides DC bias for the microcontroller, CMOS holding component, I/O expansion component, and voltage extension component. When the decoder operates below 2.7V, the linear-hold component generates a reset signal that causes the microcontroller to perform the initialization procedure. The linear hold component also includes a brownout alarm circuit, a vibration, luminous and audible alarm driver circuit, and a voltage expansion interface circuit. The microcontroller controls the operation of the entire decoder. As soon as the pager is turned on, the microcomputer component reads the content of EEPROM and issues a circuit power-up command. The microcontroller also processes the user's keystroke input and produces a liquid crystal display. The CMOS holding component communicates with the microcontroller through the SPI signal, and contains an EEPROM, which stores the pager selection and address code that the pager can respond to, which can realize online modification and power-down saving; Contains a crystal oscillator circuit connected to a 38.4kHz quartz crystal to serve as the microcontroller's clock; an internal frequency synthesizer for timing the microcontroller during data decoding; a bit synchronizer and an 8-bit accumulator to receive RF data, which cuts off the connection with the microcontroller to accumulate and synchronize the input RF signal; a 3.2kHz audio signal generator; a key encoder and three mode timers to generate data decoding interrupt signals. The I/O expansion components are used to determine the addresses of RAM and ROM, drive the control lines of linear components, control backlight lighting circuits, and control display components. The I/O expansion component sets the corresponding output state according to the instructions of the microcontroller. Voltage expansion assemblies provide operating power to RAM, ROM, and display components, as well as all components that require power. This is probably the hardware composition of the entire Motorola pager, in terms of current cognition, the pager is actually a user receiver, which consists of a superheterodyne receiver, a decoder, a controller and a display, and the detailed hardware function block diagram can be shown in the figure below.
brief summary
From the perspective of Motorola's BB machine disassembly, this one-way communication method has been completely outdated at present, but it does not prevent it from becoming a classic at that time, and even many people rely on BB machines to get rich, of course, this is also a group of lonely braves in the early days, and the later BB machine is really 49 years into the national army, how a miserable word. So, what do you think about this classic BB machine? Welcome to leave a message to discuss.