The datasheet for a 555 says that the charge time of the timing capacitor is 0.693 times (Ra + Rb) x C, and the discharge time is 0.693 x Rb x C.

Then the discharge time is the shortest so it should be the burst time of 196us or more. You need an RC time of 196 divided by 0.693= 283us. Use a 10nF capacitor and a 30k resistor for Rb for an RC of 300us then the burst timing will be 300us x 0.693= 208us.

Add a 6.2k resistor for Ra then the charge time will be (30k + 6.2k) x 10nf x 0.693= 251us. The total cycle time is 208us + 251uS= 458us and the frequency is 1 divided by 458us= 2183Hz.

But how will you use it to turn the 56k oscillator on and off?