NSSM01 Bailey Net 90 Superloop serial module

Also known as standard serial port, the most commonly used serial communication interface. It was developed in 1970 by the EIA in collaboration with Bell Systems, modem manufacturers, and computer terminal manufacturers for serial communication. Its full name is “Technical Standard for Serial Binary Data Exchange Interface between Data Terminal Equipment (DTE) and Data Communication Equipment (DCE)”. The traditional RS-232-C interface standard has 22 wires, using the standard 25-core D socket (DB25), and later simplified to 9-core D socket (DB9). Now the 25-core socket is rarely used in applications.
RS-232 adopts unbalanced transmission mode, namely the so – called single – end communication. Because the difference between the sending level and the receiving level is only about 2V to 3V, its common-mode suppression ability is poor. Coupled with the distributed capacitance on the twisted pair, the maximum transmission distance is about 15m and the maximum speed is 20kb/s. The RS-232 is designed for point-to-point (that is, only one pair of receiving and sending devices) communication, with a driver load of 3 to 7 Kω. So RS-232 is suitable for communication between local devices.