ce. You should check the impedance, because unbalanced E1/T1 are 75 ohm, whereas most 10-MHz timing interfaces are 50 ohm, although for short cable lengths, the unbal- anced E1/T1 may still function adequately well. There is also a smaller version of BNC called mini-BNC ("mini" is relative; they are still somewhat large). SubMiniature version B (SMB) connector: This is a pluggable version of the connector com- monly found as the GNSS antenna connectors. The major difference is that SubMiniature ver- sion A (SMA) is a screw-on connector, whereas SMB is a click-on pluggable. They look like some other types of connectors, SO be careful when connecting them to equipment you are unfa- miliar with. SMB is used by some vendors to help reduce the size taken up by input/output ports on their equipment. DIN 1.0/2.3: The large size of BNC is not a major issue in a large desktop device, but for the front faceplate on a pizza box router, real estate is at a premium. Therefore, Cisco and some other equipment manufacturers use DIN 1.0/2.3 connectors for 10-MHz input/output. Although many people mix them up or assume that they are the same thing, DIN 1.0/2.3 connectors are not the same as SMB connectors. DIN 1.0/2.3 connectors are widely used in the audio/visual industry and available from vendors serving that space. They are click-on and quick-disconnect pluggable devices much like SMB, but they are not compatible. BITS and E1/T1: There are two basic forms of the traditional E1/T1 circuit commonly seen in devices. Unbalanced 75 ohm used to be widespread (two cables, one for transmit, one for re- ceive, with 75-ohm coaxial cable and commonly BNC connectors), but nowadays, the BITS in- terface on the faceplate is mostly an RJ-48c port generating a balanced signal over CAT-5 un- shielded twisted-pair cable. The impedance is 120 ohm for E1 and 100 ohm for T1, and the sig- nal is carried on pins 1, 2, 4, and 5. This system can be used to carry unframed 2-MHz signals as well. BNC Connectors The PRC/PRS is almost always equipped with 