The TCM1030 and TCM1050 dual transient-voltage suppressors are designed specifically for telephone line card protection against lightning and transients (voltage transients) induced by ac lines. One of the TIP terminals (pin 1 or 8) and one of the RING terminals (pin 4 or 5) are connected to the tip and ring circuits of a SLIC (subscriber-line interface circuit). The battery feed connections between the SLIC and the subscriber line are from the remaining TIP (pin 1 or 8) and RING (pin 4 or 5) through the TCM1030 or the TCM1050 to the tip and ring lines. Transients are suppressed between tip and ground, and ring and ground. Positive transients are clamped by diodes D1 and D2. Negative transients that are more negative than VS cause the SCRs, Q1 and Q2, to crowbar. The high holding current of the SCRs prevent dc latchup as the transient subsides.