John D Holmes possesses expertise in telephony, telecommunications, avaya, call centers, contact centers and 44 more skills. Colleagues describe him as "I worked with Darrell for three years at Umgeni Water. Darrell seamlessly made the bridge from operations into engineering. Our team specialised in getting operational information to the management level. We were multidiciplined - operating systems, instrumentation and control, electronics, networking, radio telemetry, etc. It was a pleasure working with Darrell and I would have him back on my team any day." and "I have worked with Darrell for the last two and a half years and found him to be a very knowlegable and detailed engineer who prides himself in all the work he does. He is a very skilled telephony engineer and have enjoyed my time working and indeed learning from someone who enjoys the industry he works in. He will be a benefit to whichever company he is working for."