Radio and PTT interface
The original MMSSTV Basic Operations documentation states that the PC-to-radio and PTT interfaces follow the same interface concept used by MMTTY.
MMSSTV itself therefore expects the sound-card audio path and PTT switching hardware to be configured correctly between the computer and transceiver.
COM-port PTT
Later MMSSTV versions provide control of COM-port signals including DTR, RTS and TXD. These lines could be used by suitable interfaces for transmit switching or related station control.
RTS while scan
MMSSTV added an RTS while scan option so the state of the serial-port control lines could change while an SSTV picture was being received.
This was useful for station interfaces that needed a separate control state during picture reception.
VOX tone
MMSSTV can send a tone before the SSTV picture to activate a VOX-based interface. If COM-port PTT is used, or the VOX interface responds without a lead-in tone, the original documentation explains that the VOX tone can be disabled.
- Open the TX page of Setup MMSSTV.
- Select User defined in the VOX tone section.
- Open the editor.
- Remove the tone definitions.
Program menu and shared resources
MMSSTV can launch other amateur-radio or image programs from its Program menu. The original documentation gives examples such as image editors, PSK31, RTTY and MFSK16 applications.
When Suspend is enabled, MMSSTV releases the COM port and sound card before starting the selected application. This prevents two programs from attempting to use the same hardware resources at once.
Radio commands
MMSSTV later gained a Radio Command menu and support for commands for selected radios. The Basic Operations document does not reproduce the detailed command protocol; it refers to the MMTTY manual for radio-command details.