The PC-359B call holding circuit board provides the latching function when a call is placed from a remote station on the NEM series Lamp Memory System. With this circuit board, a speaker and a "Normally Open" call button can be used as a remote station where a standard sub station cannot be used. The NEM system impedance is 20 ohms, so either use a 20 ohm speaker, or an 8 ohm speaker with the LT-1 matching transformer.