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+### The `visca` backend
+
+The VISCA backend provides control of compatible PTZ (Pan, Tilt, Zoom) controllable cameras
+via the network. This protocol has, with some variations, been implemented by multiple manufacturers
+in their camera equipment. There may be some specific limits on the command set depending on make
+and model of your equpipment.
+
+This backend can connect to both UDP and TCP based cameras.
+
+#### Global configuration
+
+The `visca` backend does not take any global configuration.
+
+#### Instance configuration
+
+| Option	| Example value		| Default value 	| Description							|
+|---------------|-----------------------|-----------------------|---------------------------------------------------------------|
+| `id`		| `5`			| `1`			| VISCA Camera address (normally 1 for network communication	|
+| `connect`	| `10.10.10.1 5678`	| none			| Camera network address and port. Default connection is TCP, when optionally suffixed with the `udp` keyword, connection will be UDP |
+| `device`	| `/dev/ttyUSB0`	| none			| (Linux only) Device node for a serial port adapter connecting to the camera |
+
+#### Channel specification
+
+Each instance exposes the following channels
+
+* `pan`: Pan axis
+* `tilt`: Tilt axis
+* `panspeed`: Pan speed
+* `tiltspeed`: Tilt speed
+* `zoom`: Zoom position
+* `focus`: Focus position
+* `memory<n>`: Call memory <n> (if incoming event value is greater than 0.9)
+
+Example mappings:
+
+```
+control.pan > visca.pan
+control.tilt > visca.tilt
+control.btn1 > visca.memory1
+```
+
+#### Known bugs / problems
+
+Value readback / Inquiry is not yet implemented. This backend currently only does output.
+
+Some manufacturers use VISCA, but require special framing for command flow control. This may be implemented
+in the future if there is sufficient interest.
+
+Please file a ticket if you can confirm this backend working/nonworking with a new make or model
+of camera so we can add it to the compatability list!