The Baycom modem is based on the TCM3105 (1200 Baud Modem IC) chip of Texas Instruments.
A Baycom modem is a simple interface to receive and transmit AFSK modulated signals connected between the transceiver and the serial port of the PC.
This is a picture of the BayCom Micro Modem for RS-232.
This modem is used for 1200Bd operation, as used on the VHF/UHF bands worldwide. The baudrate can be boosted to 2400Bd by crystal replacement.
NOTA : This modem was used since 2004 to 2008 for VHF Digipeater (F5RRS-4 on APRS Network) AX25 Packet Radio operation (1200 baud). It has been replaced by USB TNT V3.0