The MSCBT IC is a CMOS chip that has the analog signal processing functions required by cellular phones and radio and other full duplex and half duplex devices.

The MSCBT integrated circuit allows bi-directional transmit and receive gain volume and filtering for the voice band. In addition, the MSCBT provides the filter needed for Continuous Tone Control Squelch System (CTCSS) and Continuous Digital Control Squelch System (CDCSS) generation and detection. A comparator in the MSCBT allows for the recovered squelch or DTMF tones to be applied to a microcontroller for decoding.

An internal highpass filter attenuates the tones from the voice band, by 50 dB, preventing voice from effecting tone transmission. A limiter increases the voice signals to be transmitted to 2Vpp for more effective modulation. The transmit output is filtered to a selectable 2.55 or 3kHz bandwidth before gain adjusts. A differential output is provided for interface with a variety of FM transmitter choices.

The MSCBT will operate from 3.3 V to 5.5 VDC. The MSCBT is available in a 32 pin 7x7mm LQFP.


  • Function down to 3.3 VDC
  • Low Power Consumption
  • 50 CTCSS Squelch Tones filtered
  • CDCSS Code filter
  • Programmable filter for pre-detection filtering
  • Comparator for direct uP interface of detected signals


  • Family Radio Service (FRS) 2-way Radio
  • Land Mobile Radio (LMR) 2-way Radios
  • General Mobile Radio Service (GMRS) 2-way Radios
  • Low Power Radio Service (LPRS) 2-way Cellular
  • Non-standard Voice-based communications
  • Wired and Wireless Intercom
  • Half-Duplex Speakerphone Analog Signal Processing
  • Full-Duplex Speakerphone Analog Signal Processing