Not all radios have this function. Most of the very high end radios do not. Many of the least expensive radios do not have it, as well.

To take advantage of this function, both of the radios to be interconnected must be by the same maker. Preferably of the same type. Always check that the cable port on both radios is the same. Generally, radios of two different brands are not compatable. Either the design of the cable port, or the way the radio sends and receives signals will be different from another brand names' product.

It would cost more to retrofit a radio with this function than it would to buy a new one with this function already a part of the radio.