CML - Wireline Data and Telephony - FX/MX604

The FX604 is a low power CMOS integrated circuit for the reception and transmission of asynchronous 1200bps data in accordance with CCITT V.23 and ETSI specifications. It is also capable of generating the 75bits/sec 'back channel'.

The device incorporates an optional Tx and Rx data retiming function that removes the need for a UART in the associated µC when operating at 1200bps. The device can disable the back channel or be operated so only the mark or space tone is produced. An optional line equaliser is incorporated into the receive path, this is controlled by an external logic level. The FX604 may be used in a wide range of telephone telemetry systems. With a low voltage requirement of 3.0V it is suitable for both portable terminal and line powered applications. A very low current 'sleep' mode (1mA typ.) and operating current of 1mA typ. mean that the device is ideal for line powered applications. A 3.58MHz standard Xtal/Clock rate is required.

Block Diagram


  • 1200/75 bps Full Duplex V.23 Compatible Modem with: Optional 75bps Back Channel Optional 1200bps Data Retiming Facility
  • 3.58MHz Xtal/Clock Rate
  • Optional Line Equalisation
  • Conforms to Relevant Sections of V.23 and ETSI Specs


  • Automatic Meter Reading: BT SIN 236 and 237
  • Line Powered Telemetry
  • Unattended Security Systems
  • Telecommand Systems
  • Payphones; Feature Phones
  • Vending Machines
  • Marine and Amateur Radio Data

Supply Requirement:

  • 3.0 to 5.5 V power supply