V21, V23, Bell 103, Bell 212A - Low Speed Modem Software
V.21 Software (Soft Modem V21)
The GAO V.21 modem software implements the ITU V.21 recommendation for speeds up to 300bps for use in the GSTN. GAO’s implementation for this modem software uses frequency shift modulation with the symbol rate equal to the bit rate. The mean frequencies for channel 1 and 2 are 1080Hz and 1750Hz respectively. This modem software allows both synchronous and asynchronous procedures. More
V.23 Software (Soft Modem V23)
ITU-T V.23 standard is 600/1200-baud modem standardized for use in the general switched telephone network. GAO’s V.23 Modem software implements the ITU V.23 recommendation for data signaling speeds of 600bps and 1200bps using the FSK technique. The center frequencies are 1500Hz and 1700Hz. GAO’s modem software implementation also supports a backward channel of 75bps. More
Softmodem Bell103 (Bell 103 Low Speed Software)
GAO’s Bell 103 modem software implements the Bell 103 data set for up to 300bps full duplex data communication. This modem operates on two-wire systems using two distinct frequency bands for frequency modulation. This is a split channel modem, like the ITU-T V.21, which uses different frequencies. GAO’s Bell 103 softmodem can either originate or answer calls and can be used with a direct connection or by acoustic coupler. More
Softmodem Bell212A (Bell 212A Low Speed Software)
GAO’s Bell 212A softmodem implements the Bell 212A data set for up to 1200bps full duplex data communication. It functions asynchronously, utilizing PSK modulation for its 1200bps mode of operation and FSK technique for its 300bps mode of operation. It can also function as a synchronous device in the 1200bps range, and is interoperable with the GAO Bell 103 softmodem. It also supports either manual originate/answer or automatic answer. More
For ITU-T standard on V.21 & V.23, click ITU-T Standards: V.21, V.21, V.23.
For examples of GAO’s Modem Software Architecture, click GAO’s Modem Software Architecture.
For a complete list of GAO’s Modem Software products, please see GAO’s Softmodem List.