PC-based oscilloscopes consists of a specialized signal acquisition board which can be an external USB or Parallel port device, or an internal add-on PCI or ISA card. Handheld oscilloscopes or scopemeters are useful for many test and field service applications. Some instruments combine the functions of a digital multimeter with the oscilloscope. These usually are lightweight and have good accuracy. Digital storage oscilloscopes or DSO for short, is now the preferred type for most industrial applications. A digital storage oscilloscope also allows complex processing of the signal by high-speed digital signal processing circuits. Digital sampling oscilloscopes are for measuring repetitive signals, this type can have bandwidth and high-speed timing up to ten times greater than any real-time oscilloscope.