SRV4 4-Way Model Railway Servo Controller for Points & Signals

About the Product

The BLOCKsignalling SRV4 is a 4-way model railway servo controller for points, signals, gates and other layout accessories, providing independent control of up to four miniature analogue servos with adjustable start position, stop position and movement speed.

Each servo can be operated using switches, push buttons, stud-and-probe control or a compatible DCC accessory decoder, making the SRV4 suitable for both conventional control panels and DCC-controlled model railway layouts.

The module also provides outputs for two-aspect signals and control-panel LEDs, together with connections for optional 5V relays that can automatically switch live frog polarity as servo-operated points change position.

Key Features

• Controls up to four miniature analogue servo motors.
• Ideal for model railway points, signals, gates, barriers and other moving accessories.
• Independently programmable Start and Stop positions for each servo.
• Adjustable servo movement speed.
• Operates from switches, push buttons or stud-and-probe control.
• Can be connected to DCC accessory decoders for DCC servo control.
• Outputs for two-aspect model railway signals.
• Outputs for control-panel LEDs.
• Supports both common-anode and common-cathode LED signals.
• Optional relay outputs for automatic live frog polarity switching.
• Each relay output changes state as its associated servo passes its mid-position.
• Compatible with miniature analogue servos such as Tower Pro 9g types.
• Settings are stored by the module after programming.
• Requires a regulated 12V DC power supply.
• Quick and straightforward setup using the built-in controls and programming button.

Four Independent Servo Outputs

The SRV4 can control up to four miniature analogue servos, with each servo moving between its individually programmed Start and Stop positions.

This makes the controller particularly useful for operating model railway points and turnouts, but the servos can also be mechanically connected to semaphore signals, crossing gates, barriers and other moving layout features.

The SRV4 is designed for miniature analogue servos, including types such as the Tower Pro 9g or similar.

Servo Connections

Adjustable Position & Movement Speed

Each servo can be individually programmed for its required:

• Start Position: Sets one end of the servo movement.
• Stop Position: Sets the opposite end of the servo movement.
• Movement Speed: Controls how quickly the servo travels between the two positions.

This allows the amount and speed of movement to be matched to the accessory being operated, rather than requiring the servo to move through its full mechanical range.

The settings are adjusted using the START, STOP and RATE controls built into the SRV4 and are then stored for each servo.

Switch, Push Button & DCC Control

Each servo has two control inputs, allowing it to be moved between its Start and Stop positions.

The inputs can be operated using momentary push buttons, permanent switches or stud-and-probe control.

The SRV4 can also be connected to the outputs of a DCC accessory decoder, allowing the servos to be operated from a DCC system without requiring a dedicated servo decoder.

Automatic Frog Polarity Switching

When servos are used to operate model railway points, an optional 5V relay can be connected for each servo to control live frog polarity.

The appropriate relay output changes state when the servo passes its mid-position, allowing the frog polarity to change automatically as the point moves.

Compatible relays require a 5V coil drawing less than 100mA.

Example Points Wiring

Signal & Control Panel LED Outputs

The SRV4 includes LED outputs that can be used to provide a visual indication of each servo position.

Up to four LEDs can be connected for each servo, allowing indicators to be fitted to a control panel while also operating a two-aspect signal.

Both common-cathode and common-anode signals can be connected. The LED outputs change automatically according to the position of the associated servo.

Existing resistors fitted to LEDs or signals can normally remain in place, although the SRV4 does not require an additional resistor for LEDs connected as described in the instructions.

Electrical Requirements

• Power Supply: 12V DC.
• Maximum Current Consumption: Up to 1A.
• Recommended Power Supply Rating: 1A to 2A.
• Servo Capacity: Up to four miniature analogue servos.
• Relay Coil Voltage: 5V.
• Maximum Relay Coil Current: 100mA.

Do not power the SRV4 from the auxiliary output of a train controller. These outputs may not provide a sufficiently smooth or stable supply for the module. 

What's Included

• BLOCKsignalling SRV4 Servo Controller.

Servos, relays, LEDs and power supply are not included.

Documentation & Support

For full installation instructions, wiring diagrams, servo setup, programming options and troubleshooting information, please refer to the Product documents section below.

Product Instruction Manual