D-Sub and DB are prefixes used to describe a type of multi-pin connectors that happen to be commonly used in audio equipment. The original manufacturer, ITT Cannon, adopted the “D” designation as the lead character in their part numbers signifying the connector type. The shell size, or capacity, is next in the part number: A=15 pin, B=25 pin, C=37 pin, D=50 pin and E=9 pin (not originally produced). This type connector can also be specified with many different styles and quantities (up to its capacity) of pin: high power, coax and combinations. The most common connector, early on, was the 25-pin size, which was used on RS232 ports (a common computer port). Hence DB25M means “D” type, “B” shell, 25 pins, Male pin. Note that a 15-pin female would be DA15F. D-Sub is short for the current industrial tag, D-Subminiature, used by almost all of the manufacturers.