Model Railway Four Block Signal Controller - Code: RK-SBP4

This unit controls two or three colour signals protecting blocks along a single direction track. A unit controls four blocks, and hence four signal masts.

The unit requires input from detectors at the start of each block. Two D2 units are required per SBP4 unit. These may be cuurent, infrared, light, or magnetic, according to user preference.

When a train is detected, the corresponding block signal is set to stop, and remains so until the train passes into the next block. Even though a train is detected in the next block, the signal will continue to display stop in the current block for as long as a train is being detected in that block.

As a train proceeds from block to block, the controller causes the signal to display stop, caution, clear in sequence. The aspects displayed are shown in the table below right.

A jumper on the Printed Circuit Board (PCB) is used to select whether each of the four signal masts individually is two colour or three colour. A searchlight signal is treated as a two colour signal, and is implemented using a Red/Green LED, with the yellow generated by having both red and green elements on at the same time.

The unit provides output to drive either common anode or common cathode Light Emitting Diode (LED) displays directly. (But NOTE: all signals on the one controller must have the same commonality.) Many commercially available Signal Masts will accept 3mm LEDs, or a modeller may elect to construct his/her own.

Multiple units are designed to be interconnected. (A Block Occupied - BO - output from one unit is fed to the Next Block In - NBI - input on the previous unit) However, this interconnection may be left out, and by means of a jumper, the units may function on a time delay.

If the four blocks are on a circular track, then BO may be connected to NBI on the same unit, setting up a four block circular control.

In the diagram at right, two detetcors are shown using a D2L (light) detector, and 2 using a D2C (current) detector. This would not be the normal means of detection, although the user may use any combination of detector types as is conveninet in the situation, provided the detectors are arranged sequentially such that D1 is the first detector passed by the train, and D4 is the last. The combination of detectors is shown to make the point that any detectors may be used. Similarly, different signal masts (2,3 colour, searchlight) are shown to indicate that any combination of types may be used.

Kit price for           RK-SBP4: $31-00
Kit price for         RK-D2C/IR/L/M : $22-50

All kits available from :
Aztronics Pty Ltd       Phone 8212 6212
170 Sturt St,                     Fax 8212 4212
Adelaide, SA, 5000.                                

Click here to go to Aztronics web site

Information:         David Crosby

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Last updated 3rd February, 2017.
(C) D. Crosby, June, 2011.