# TimerSignalHeartbeatVBL

Sends a signal periodically based on VBLs.

### Synopsis

`TimerHandle TimerSignalHeartbeatVBL (int32 signal, uint32 fields)`

### Description

Creates a timer that repeatedly notifies you by signal after the specified number of VBLs have occurred. The timer continues sending notifications on a regular interval until you use `TimerSuspend()` to temporarily halt it or `TimerCancel()` to delete it.

The Heartbeat support in the TimerServices thread contains logic to prevent drift in the frequency of timer events. Signals are delivered at the specified frequency even if it takes you significant time to respond to each signal event.

The TimerServices thread must be active before calling this function.

### Arguments

signal
  Signal to send to your task.

fields
  Number of VBLs to occur between each event.

### Return Value

A TimerHandle (a positive value) on success or a negative error code.

### Implementation

Library call implemented in lib3do.lib.

### Associated Files

lib3do.lib, timerutils.h

### See Also

`TimerSignalAtTimeVBL`, TimerSignalAfterDelayVBL