Praktika T-04(K) speedgate
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Appendix 1. Summary of the data bus CAN2.0
The RC panel uses modern CAN2.0 noise-immune bus. According to
CAN2.0 standard signal cable length can exceed one kilometer, however
correct operation on these distances depends on many factors. Always use
Cat5e or Cat6 twisted pair at distances exceeding 25 meters. The total
electrical resistance of DC power supply wire shall not exceed 50 ohms. If
this requirement cannot be met an additional 12V / 100mA power supply
unit (minimum operating voltage of PU - 7.5V). There are 3wires - CL,
CH, GND - enough for the correct operation of speedgate. In this case the
power supply wire from the PU to the speedgate is not required. See Fig.
18. Two RC panels can be connected to the same speedgate.
An important feature of the CAN2.0 bus is the use of 120 Ohm
resistors at the ends of the bus. The standard RC panel is equipped with
such resistor on default. If you use one RC panel it is recommended to
connect an additional (second) 120 ohm resistor mounted on the
motherboard to CL and CH terminals. It is connected with the use of J4
jumper. Installation process is described in article 5.3 (Connecting side
units).
It is not required, however, in case of connection of two RC panels,
because required 120 ohm resistors are already installed at the ends of the
bus (in RC panels).
A special RC panel is required to operate several speedgates
simultaneously. Standard RC is not appropriate for this purpose.
