Videcom Pelco Telemetry Explained.

Pelco Pelco is one of the world's brand leaders in the design manufacture and delivery of high end CCTV and security products. Many CCTV manufactures use the commonly used Pelco Telemetry protocols to allow integration of their CCTV onto a wider range CCTV control systems. Pelco D and Pelco P are both RS485 data protocols for controlling PTZ moveable cameras, typically found on analogue cameras we have seen some implementation of Pelco P on IP HD CCTV cameras. This help page describes how the Pelco telemetry works and how the RS485 data packets are put together.

The Videcom VNR supports both Pelco Telemetry output for analogue CCTV camera control as well as RS485 Pelco telemetry to ONVIF conversion for integration with legacy CCTV systems. This additional integration allows for Pelco Telemetry from existing systems to control almost any ONVIF PTZ Camera.

Pelco D Pelco-D consists of 7 hexadecimal bytes, a hex byte is a 2 digit number that can represent a value from 00 to 255, 0h to FFh. The telemetry message sent to the camera consists of a start (STX) the commands then a Checksum and the end of the message (ETX). At first this can appear complicated but as we break the message string down it becomes easier to understand.

Byte 0 Byte 1 Byte 2 Byte 3 Byte 4 Byte 5 Byte 6
STX Camera Number Command 1 Command 2 Data 1 Data 2 Checksum
FF 1C 00 00 00 00 FF

Data 1This sends the Pan speed and provides a proportional speed control 00 (stop) to 3F(63) and for FULL SPEED turbo FF (255).
Data 2This sends the Tilt speed and provides a proportional speed control 00 (stop) to 3F(63).

The command bytes are slightly more complicated and depending on the command the data bytes can be used for other functions, for example when recalling presets. Each Command Byte is made up from the following Bits (8 bits makes a byte)

Pelco D Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
Command 1 Sense Reserved Reserved Auto Pan Cam On/Off Iris Close Iris Open Focus Near
Command 2 Focus Far Zoom Out Zoom In Tilt Down Tilt UP Pan Left Pan Right Set to 00h


Pelco P Pelco-P consists of 8 hexadecimal bytes, with a different (STX) and (ETX) coding AOh & AFh, also the camera numbers of offset by 1 this allows for an additional address as 00h is used for camera 1,

Byte 0 Byte 1 Byte 2 Byte 3 Byte 4 Byte 5 Byte 6 Byte 7
STX Camera Number Command 1 Command 2 Data 1 Data 2 ETX Checksum
A0 1C 00 00 00 00 AF BB

Data 1This sends the Pan speed and provides a proportional speed control 00h (stop) to 3Fh(63) and for FULL SPEED turbo 40h (64).
Data 2This sends the Tilt speed and provides a proportional speed control 00h (stop) to 3Fh(63).

The command bytes are slightly more complicated and depending on the command the data bytes can be used for other functions, for example when recalling presets. Each Command Byte is made up from the following Bits (8 bits makes a byte)

Pelco P Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
Command 1 Reserved Cam On/Off Auto Pan Auto Pan Iris Close Iris Open Focus Near Focus Far
Command 2 Reserved Zoom Out Zoom In Tilt Down Tilt UP Pan Left Pan Right Set to 00h