 
 	// TODO: 8.0+ only
 	public func peripheral(_ peripheral: CBPeripheral, didReadRSSI RSSI: NSNumber, error: Error?) {
-		self.operationQ.async(execute: { () -> Void in
+		operationQ.async(execute: { () -> Void in
 			for req in self.RSSIRequests {
 				req.timedOut = false
 				DispatchQueue.main.async(execute: { () -> Void in

	*						they can be retrieved via <i>service</i>'s <code>characteristics</code> property.
	*/
	public func peripheral(_ peripheral: CBPeripheral, didDiscoverCharacteristicsFor service: CBService, error: Error?) {
		self.operationQ.async { () -> Void in
			// multiple reqs of discovering characteristic within a short duration will be responsed simultaneously
			// 1. check if characteristic UUID specified in req...
			for req in self.characteristicDiscoveringRequests {

	*
	*/
	public func peripheral(_ peripheral: CBPeripheral, didDiscoverServices error: Error?) {
		operationQ.async { () -> Void in
			// multiple reqs of discovering service within a short duration will be responsed simultaneously
			// 1. check if service UUID specified in req...
			for req in self.serviceDiscoveringRequests {
