Most video recorders were also unable to change channels under control of built-in timers when using a converter, as channel selection was then handled by the converter. Some converter boxes have a programmable timer, which the user could program to match the recording schedule of their VCR. Then, the converter's tuner will change to the appropriate channel at the time the VCR needs to record. This requires a separate box for the VCR, or the viewer will have to watch what is being recorded. Another, less common option is an "IR blaster", which a recorder can use to control an external tuner, like a cable set-top box or converter box. However, older devices with IR blasters may not be fully compatible with digital subchannels; the converter box may require the use of a [-] or [.] button to specify the subchannel, which the pre-digital recorder may not know how to transmit. Some older TiVo brand digital recorders received software updates specifically to control digital converter boxes via the TiVo's included IR blaster.